Tidy the introduced-in line for cherry-picking

Small fixes to the introduced-in line for cherry-picking into a
project. Punctuation, linking.

doc/user/project/merge_requests/cherry_pick_changes.md

@@ -62,8 +62,8 @@ git cherry-pick -m 2 7a39eb0
 
 ### Cherry-pick into a project
 
-> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/21268) in GitLab 13.11.
-> - [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/issues/324154) in GitLab 14.0
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/21268) in GitLab 13.11 behind a [feature flag](../../feature_flags.md), disabled by default.
+> - [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/issues/324154) in GitLab 14.0.
 
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