Exclude internal API and Geo git_ssh routes from secondary proxying

What does this MR do and why?

The api/internal routes need to not be proxied to allow detection if the repository exists locally for a project, and redirection to the primary if not.

The geo/proxy_git_ssh route is used internally by gitlab-shell to then proxy the git+ssh operations to the primary, using the internal URL of the primary (hence why these don't get proxied and is intended that they hit the secondary).

Related to #343537 (closed) and #342601 (closed).

Screenshots or screen recordings

How to set up and validate locally

1. With a Unified URL Geo set up (GET at the moment), stop Sidekiq on the secondary node, and always point the URL to the secondary (/etc/hosts or similar)
2. Create a new project through the UI (which should create it on the primary)
3. Attempt to pull/push through SSH and notice errors
4. Checkout this branch, make and scp the gitlab-workhorse binary to the GET Geo secondary Rails node, restart workhorse, then redo the tests and notice these are working

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