Merge branch 'docs-ssh-newline-note' into 'master'

Add troubleshooting for SSH keys in CI

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/137213



Merged-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Manuel Grabowski <mgrabowski@gitlab.com>
Co-authored-by: Marcel Amirault <mamirault@gitlab.com>