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)

app/controllers/projects/commits_controller.rb

@@ -91,7 +91,7 @@ def set_commits
         @repository.commits(ref, **options)
       end
 
-    @commits.load_tags if Feature.enabled?(:show_tags_on_commits_view, @project)
+    @commits.load_tags
     @commits.each(&:lazy_author) # preload authors
 
     @commits = @commits.with_markdown_cache.with_latest_pipeline(ref)