Remove unused rugged code that is currently on Gitaly

lib/gitlab/git/repository.rb

@@ -1253,14 +1253,6 @@ module Gitlab
         run_git(args, env: source_repository.fetch_env)
       end
-      def rugged_add_remote(remote_name, url, mirror_refmap)
-        rugged.remotes.create(remote_name, url)
-
-        set_remote_as_mirror(remote_name, refmap: mirror_refmap) if mirror_refmap
-      rescue Rugged::ConfigError
-        remote_update(remote_name, url: url)
-      end
-
       def gitaly_delete_refs(*ref_names)
         gitaly_ref_client.delete_refs(refs: ref_names) if ref_names.any?
       end