Remove pages_serve_from_deployments FF
Currently, we use feature flag to allow serving from pages deployments - https://gitlab.com/gitlab-org/gitlab/blob/8c644ff81d09a1d7bc0c3630fad51d30e6d198d8/app/models/pages/lookup_path.rb#L49
If migration on self-hosted install will be finished, we can simply remove this feature flag and make it enabled by default
Edited by Vladimir Shushlin