Clean up feature flag for release path fix

What does this MR do and why?

The merge request is to cleanup the fix_release_path_in_tag_index_page feature flag, after the feature flag has been enabled globally for an appropriate amount of time on production. The logs and the release stage dashboard were monitored over the last 24 hours to ensure everything works as expected, and there has been no reported issues since the flag was enabled.

Please refer to the original issue, the merge request introducing the feature flag, and the rollout issue for more information.

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