Rename UrlBlocker argument: schemes -> protocols

This was renamed in GitLab 11.11, so the backport needs to use
the original name.

lib/gitlab/url_blocker.rb

@@ -23,7 +23,7 @@ module Gitlab
       def validate!(
         url,
         ports: [],
-        schemes: [],
+        protocols: [],
         allow_localhost: false,
         allow_local_network: true,
         ascii_only: false,