Remove show_tags_on_commits_view feature flag

What does this MR do and why?

Removes show_tags_on_commits_view feature flag. It's been default enabled since 15.10 and the feature seems stable.

How to set up and validate locally

1. Create some commits
2. Add tag to a commit
3. Add multiple tags to a different commit
4. Check the commits view (e.g http://127.0.0.1:3000/root/project/-/commits/main) and see that the tag badges appear next to the correct commits

Should look like this:

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #397738 (closed)