Documentation issue; Repository checks on Kubernetes
<!--IssueSummary start-->
<details>
<summary>
Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards.
</summary>
- [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=374503)
</details>
<!--IssueSummary end-->
### Problem to solve
Documentation at https://docs.gitlab.com/ee/administration/repository_checks.html for Gitlab deployments on kubernetes is incomplete/provides no way forward.
### Further details
I run Gitlab on site on Kubernetes using the helm deployment and recently ran into a repository check failure.
By checking the documentation at https://docs.gitlab.com/ee/administration/repository_checks.html, I was able to find the repocheck.log in the sidekiq pod, but then it goes on to say "Run a check using the command line" and says to do this in the gitaly pod and gives the command `sudo -u git /opt/gitlab/embedded/bin/git -C /var/opt/gitlab/git-data/repositories/@hashed/0b/91/0b91...f9.git fsck`.
This does not work. Firstly; there is no `sudo` in the gitaly pod and you log in as the git user, so you don't need it anyway. Secondly; there is no `git` in the gitaly pod (!!) - that is, the binary is nowhere to be found. The only way I was finally able to fix the repocheck issue was by copying the git binary from my system into the pod using `kubectl cp` and running the commands with that.
### Proposal
The documentation needs to be amended to clarify what to do in the gitaly pod on a Kubernetes deployment for gitlab, as the current instructions don't work.
It might also be a good idea to include a git binary into the image itself... but that is probably an issue for a different sub-tracker.
issue