Add SSH example that provides a port number

What does this MR do?

Some folks need to specify a port number when SSHing. Adds an example + explanation for how to do this. When reported in #248570 (closed) the problem was in doc/gitlab-basics/create-project.md#push-to-create-a-new-project. It's since moved to doc/user/project/index.md#create-a-new-project-with-git-push but the need is still valid.

Thanks, @bancarel.valentin - I found this issue as part of doing cleanup + triage on old groupcode review / devopscreate issues.

Related issues

Closes Docs feedback: Add standard ssh syntax (non scp... (#248570 - closed)

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