Improve Vale badge capitalization rule

What does this MR do?

This MR:

• changes the matching from sass to saas (acronym for software as a service)
• captures other capitalizations as noted in the original MR:

  I'll see if I can look for any lowercase letter in a future update

References:

• Current list of available product tier badges

I have already ran Vale on the latest documentation, and no changes need to be made in the docs

/cc @marcel.amirault

How to setup and validate locally

1. Run vale doc/
2. Check for ✔ 0 errors, 0 warnings and 0 suggestions in 1304 files.
3. Run vale test.md (test.md content provided below)
4. Check for ✖ 27 errors, 0 warnings and 0 suggestions in 1 file. (errors are expected)

test.md:

| Input                 | Result expected | Result before | Result after | Correct before | Correct after |
| --------------------- | --------------- | ------------- | ------------ | -------------- | ------------- |
| `**(FREE)**`          | negative        | negative      | negative     | yes            | yes           |
| `**(PREMIUM)**`       | negative        | negative      | negative     | yes            | yes           |
| `**(ULTIMATE)**`      | negative        | negative      | negative     | yes            | yes           |
| `**(FREE SELF)**`     | negative        | negative      | negative     | yes            | yes           |
| `**(PREMIUM SELF)**`  | negative        | negative      | negative     | yes            | yes           |
| `**(ULTIMATE SELF)**` | negative        | negative      | negative     | yes            | yes           |
| `**(FREE SAAS)**`     | negative        | negative      | negative     | yes            | yes           |
| `**(PREMIUM SAAS)**`  | negative        | negative      | negative     | yes            | yes           |
| `**(ULTIMATE SAAS)**` | negative        | negative      | negative     | yes            | yes           |
| `**(FREE SAAS)**`     | negative        | negative      | negative     | yes            | yes           |
| `**(FREE SASS)**`     | negative        | negative      | negative     | yes            | yes           |
| --------------------- | --------------- | ------------- | ------------ | -------------- | ------------- |
| `**(free)**`          | positive        | positive      | positive     | yes            | yes           |
| `**(premium)**`       | positive        | positive      | positive     | yes            | yes           |
| `**(ultimate)**`      | positive        | positive      | positive     | yes            | yes           |
| `**(free self)**`     | positive        | positive      | positive     | yes            | yes           |
| `**(premium self)**`  | positive        | positive      | positive     | yes            | yes           |
| `**(ultimate self)**` | positive        | positive      | positive     | yes            | yes           |
| `**(free saas)**`     | positive        | negative      | positive     | no             | yes           |
| `**(premium saas)**`  | positive        | negative      | positive     | no             | yes           |
| `**(ultimate saas)**` | positive        | negative      | positive     | no             | yes           |
| `**(free sass)**`     | negative        | positive      | negative     | no             | yes           |
| --------------------- | --------------- | ------------- | ------------ | -------------- | ------------- |
| `**(Free)**`          | positive        | positive      | positive     | yes            | yes           |
| `**(Premium)**`       | positive        | positive      | positive     | yes            | yes           |
| `**(Ultimate)**`      | positive        | positive      | positive     | yes            | yes           |
| `**(Free Self)**`     | positive        | positive      | positive     | yes            | yes           |
| `**(Premium Self)**`  | positive        | positive      | positive     | yes            | yes           |
| `**(Ultimate Self)**` | positive        | positive      | positive     | yes            | yes           |
| `**(Free Saas)**`     | positive        | negative      | positive     | no             | yes           |
| `**(Premium Saas)**`  | positive        | negative      | positive     | no             | yes           |
| `**(Ultimate Saas)**` | positive        | negative      | positive     | no             | yes           |
| `**(Free Sass)**`     | negative        | positive      | negative     | no             | yes           |
| --------------------- | --------------- | ------------- | ------------ | -------------- | ------------- |
| `**(FrEe)**`          | positive        | negative      | positive     | no             | yes           |
| `**(PrEmIuM)**`       | positive        | negative      | positive     | no             | yes           |
| `**(UlTiMaTe)**`      | positive        | negative      | positive     | no             | yes           |
| `**(FrEe SeLf)**`     | positive        | negative      | positive     | no             | yes           |
| `**(PrEmIuM SeLf)**`  | positive        | negative      | positive     | no             | yes           |
| `**(UlTiMaTe SeLf)**` | positive        | negative      | positive     | no             | yes           |
| `**(FrEe SaAs)**`     | positive        | negative      | positive     | no             | yes           |
| `**(PrEmIuM SaAs)**`  | positive        | negative      | positive     | no             | yes           |
| `**(UlTiMaTe SaAs)**` | positive        | negative      | positive     | no             | yes           |
| `**(FrEe SaSs)**`     | negative        | negative      | negative     | yes            | yes           |

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.