Remove tier badging from doc links on index page

What does this MR do?

In gitlab-docs!1393 (merged) we removed the tier badges from the global nav, as the documentation pages themselves should be used as the SSOT for noting which features are in which tiers. I've also noticed that index pages have tier badge information on them, likely because of /help and its use of index pages to allow users to find pages. Removing the tier badges from the index pages should happen in a similar fashion as that of their removal from the global nav.

This MR removes the tier badge mentions from the doc page links. Readers can continue to determine the tier availability of a feature by visiting its doc page, utilizing the concept of SSOT for maintenance of this info, and also encouraging users to learn about features they may not have access to at their subscription level.

(I also removed a link to a doc about Pivotal that's now EoL. The doc is still in place, but it didn't make sense to list it on this index page.)

If you have any questions or concerns about this, please let me know, but I at least wanted to get the MR in place.

Related issues

gitlab-docs!1393 (merged)

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.
• If you have Developer permissions or higher:
  • Ensure that the product tier badge is added to doc's h1.
  • Apply the documentation label, plus:
    • The corresponding DevOps stage and group labels, if applicable.
    • development guidelines when changing docs under doc/development/*, CONTRIBUTING.md, or README.md.
    • development guidelines and Documentation guidelines when changing docs under development/documentation/*.
    • development guidelines and Description templates (.gitlab/*) when creating/updating issue and MR description templates.
  • Assign the designated Technical Writer.

Do not add the feature, frontend, backend, ~"bug", or database labels if you are only updating documentation. These labels will cause the MR to be added to code verification QA issues.

When applicable:

• Update the permissions table.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Add the product tier badge accordingly.
• Add GitLab's version history note(s).
• Add/update the feature flag section.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.
  • Ensure docs metadata are present and up-to-date.
  • Ensure Technical Writing and documentation are added.
  • Add the corresponding docs:: scoped label.
  • If working on UI text, add the corresponding UI Text scoped label.
  • Add twdoing when starting work on the MR.
  • Add twfinished if Technical Writing team work on the MR is complete but it remains open.

For more information about labels, see Technical Writing workflows - Labels.

For suggestions that you are confident don't need to be reviewed, change them locally and push a commit directly to save others from unneeded reviews. For example:

• Clear typos, like this is a typpo.
• Minor issues, like single quotes instead of double quotes, Oxford commas, and periods.

For more information, see our documentation on Merging a merge request.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.