Refactor SSH keys docs for Windows clients
What does this MR do?
Refactors the SSH keys docs for Windows clients. I opted to drop the CMD/PowerShell options and use tooling that allows us to provide universal commands. Convention over configuration :)
What are the relevant issue numbers?
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/46399 https://gitlab.com/gitlab-org/gitlab-ce/issues/46398