Remove deprecated templates endpoints in V4
What does this MR do?
Remove the following deprecated endpoints on V4 (and also remain these untouched on V3):
- /licences - /licences/:key - /gitignores - /gitlab_ci_ymls - /dockerfiles - /gitignores/:key - /gitlab_ci_ymls/:key - /dockerfiles/:key
Are there points in the code the reviewer needs to double check?
/dockerfiles/:name also have been deprecated on V3 and removed on V4.
- Changelog entry added
- Documentation created/updated
- API support added
- Added for this feature/bug
- All builds are passing
- Conform by the merge request performance guides
- Conform by the style guides
Branch has no merge conflicts with
master(if it does - rebase it please)
- Squashed related commits together
What are the relevant issue numbers?
EE-backport: gitlab-ee!1214 (merged)
Closes #22818 (closed)