Gitlab::Git::Wiki tries to call Gollum clear_cache in Rails

https://gitlab.com/gitlab-org/gitlab-ce/blob/e79f3728edddaa37c678db11824edbf4f01db63e/lib/gitlab/git/wiki.rb#L28-59

We have three methods in Gitlab::Git::Wiki that try to do the following on the client (Rails) side:

        @repository.gitaly_migrate(:wiki_write_page) do |is_enabled|
          if is_enabled
            gitaly_write_page(name, format, content, commit_details)
            gollum_wiki.clear_cache

That is never going to work, we can't instantiate a Gollum::Wiki on the client side because that needs disk access to the repository.

Reported in https://gitlab.com/gitlab-org/gitlab-ce/issues/44279