Remove outdated code for AutoDeployBranchService

The version method was reintroduced at some point, but never actually used.

The gitlab_ops_client method from BranchCreation was only used in one place, so we've localized it.

We've also stopped updating CI variables on production, since everything is now on ops.

987156c1 - Remove client argument from create_branch_from_ref

This removes the need for the same argument to latest_successful_ref, which will remove the need for the argument from Commits.new.