Remove the `container_registry_cleanup` feature flag

It has been enabled by default for a few milestones

app/services/projects/container_repository/cleanup_tags_service.rb

@@ -4,7 +4,6 @@ module Projects
   module ContainerRepository
     class CleanupTagsService < BaseService
       def execute(container_repository)
-        return error('feature disabled') unless can_use?
         return error('access denied') unless can_destroy?
         return error('invalid regex') unless valid_regex?
 
@@ -74,10 +73,6 @@ module Projects
         can?(current_user, :destroy_container_image, project)
       end
 
-      def can_use?
-        Feature.enabled?(:container_registry_cleanup, project, default_enabled: true)
-      end
-
       def valid_regex?
         %w(name_regex_delete name_regex name_regex_keep).each do |param_name|
           regex = params[param_name]

config/feature_flags/development/container_registry_cleanup.yml

----
-name: container_registry_cleanup
-introduced_by_url: 
-rollout_issue_url: 
-group: 
-type: development
-default_enabled: true

spec/services/projects/container_repository/cleanup_tags_service_spec.rb

@@ -12,8 +12,6 @@ RSpec.describe Projects::ContainerRepository::CleanupTagsService do
   before do
     project.add_maintainer(user)
 
-    stub_feature_flags(container_registry_cleanup: true)
-
     stub_container_registry_config(enabled: true)
 
     stub_container_registry_tags(