Merge branch '432439_update_ssh_docs' into 'master'

Update the documentation to clarify that SSH username can be different

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138160



Merged-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Approved-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Co-authored-by: Vasilii Iakliushin <viakliushin@gitlab.com>