Replace hardcoded N+1 specs with n_plus_one_shared_examples.rb
And consider bringing one or more custom matchers in from the monolith
The following discussion from !2278 should be addressed:
- [ ] @leetickett-gitlab started a [discussion](https://gitlab.com/gitlab-org/developer-relations/contributor-success/contributors-gitlab-com/-/merge_requests/2278#note_3403475338):
> In a follow-up let's use this for any other N+1 specs in the project :rocket:
cc @Taucher2003
issue