Remove the container_registry_expiration_policies_caching feature flag

Enabling caching for cleanup policies as described in
https://gitlab.com/gitlab-org/gitlab/-/issues/339129

Changelog: other

app/services/projects/container_repository/cleanup_tags_service.rb

@@ -146,8 +146,7 @@ module Projects
 
       def caching_enabled?
         container_expiration_policy &&
-          older_than.present? &&
-          Feature.enabled?(:container_registry_expiration_policies_caching, @project)
+          older_than.present?
       end
 
       def throttling_enabled?

config/feature_flags/development/container_registry_expiration_policies_caching.yml

----
-name: container_registry_expiration_policies_caching
-introduced_by_url:
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/340606
-milestone: '14.3'
-type: development
-group: group::package
-default_enabled: false