Check if Geo is enabled before saving enabled git access protocols

Proposal

As per https://docs.gitlab.com/ee/administration/geo/replication/configuration.html#step-5-enable-git-access-over-httphttps, Geo requires the HTTP(S) git protocol to be enabled for replication to work:

Geo synchronizes repositories over HTTP/HTTPS, and therefore requires this clone method to be enabled.

However, if an admin decided to disable HTTP via enabled Git access protocols - they could unintentionally break Geo replication.

GitLab should perform a check before saving to see if Geo is enabled. If Geo is enabled, and the user attempted to disable the HTTP(S) git protocol, block the save.