Remove project tags
We have project tags! You can set them in edit project.
As far as I can tell, these are only used on https://gitlab.com/explore/projects. On the RHS there is a tag list:
- It's huge.
- It's loaded on page load, which makes the page take 13 seconds.
- It has a terrible UX.
- We should kill it.
We removed the counter caches in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9467, but we should probably just kill project tags completely.