Disable the find_remote_root_refs_inmemory feature flag

Having this feature flag default enabled without following
the rollout process broke the Geo replication for empty
repositories.

config/feature_flags/development/find_remote_root_refs_inmemory.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/329664
 milestone: '13.12'
 type: development
 group: group::gitaly
-default_enabled: true
+default_enabled: false