Update security config documentation

What does this MR do?

Update the "Security Configuration" page's documentation to match the current UI:

• Remove mention of AutoDevOps. This was moved to another part of the UI.
• Removed some duplicate content about the UI page's content.
• Edited all UI navigation instructions to the current standard.
• Change all instances of see to read as this could be interpreted as exclusive language (WRT those with sight issues).
• Change all instances of Click to Select.
• Move the content of the Status section to the introduction. There is no reason to have it listed separately.

Related issues

#331478 (closed)

Author's checklist

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

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

• ~"feature"
• ~"frontend"
• ~"backend"
• ~"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 above reviews. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.