Clarify conditions that make code owner approvals optional

What does this MR do?

Use simpler terms to clarify when approval rules for code owners are marked as optional. Using the word not in sentences multiple times is confusing and in this case, it was misleading.

A Code Owner approval rule is optional if these conditions are not met:

• The user or group are not a member of the project or parent group.
• Code Owner approval on a protected branch has not been set up.
• The section is marked as optional.

The statement above is interpreted to mean that a Code Owner approval rule would be optional if

• The user or group are a member of the project or parent group.
• Code Owner approval on a protected branch has been set up.
• The section is not marked as optional.

because of the clause if these conditions are not met.

For example The user or group are not a member of the project or parent group. condition is NOT met when they are a member. Which is incorrect.

/cc @joseph

Related issues

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• Ensure that the product tier badge is added to topic's h1.
• Request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Review checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the reviews above. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.