Enable requiring API authentication for GET CI Lint endpoint

What does this MR do and why?

Remove the feature flag ci_require_api_token_for_ci_lint and enable authentication check to the GET :id/ci/lint endpoint to ensure requests are made with proper API authentication when a user session exists.

References

• [FF] `ci_require_api_token_for_ci_lint` -- Requ... (#578076)
• Require API authentication for GET CI Lint endp... (!209764 - merged)

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