Scope third_party_wikis by category
This issue was created from this [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82616#note_879016670).
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82616 merges contains a data migration to change the `category` of the third party integrations to `"third_party_wiki"`.
In the milestone after https://gitlab.com/gitlab-org/gitlab/-/merge_requests/82616 merges, the `third_party_wikis` scope in `app/models/integration.rb` should be changed to select third party wikis by `category: 'third_party_wiki'`.
issue