Remove unused GeoGitAccess method

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Follow up from !56280 (comment 529883165)

Michael Kozono 🔶 @mkozono · 1 day ago Maintainer

Ah interesting. I think GeoGitAccess#push_to_read_only_message ("Please use the primary node URL instead") is dead code.

As long as https://gitlab.com/gitlab-org/gitlab/-/blob/b8b972849fce9aecda364d4f2749e2f6aa56c757/ee/app/controllers/ee/repositories/git_http_client_controller.rb and https://gitlab.com/gitlab-org/gitlab/-/blob/b8b972849fce9aecda364d4f2749e2f6aa56c757/ee/lib/gitlab/geo/git_ssh_proxy.rb correctly redirect/proxy Git push requests to the primary.

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