Block external fork mirrors

Changelog: fixed

config/feature_flags/development/block_external_fork_network_mirrors.yml

----
-name: block_external_fork_network_mirrors
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/60735
-rollout_issue_url: 
-milestone: '14.0'
-type: development
-group: group::source code
-default_enabled: true

ee/app/models/ee/project.rb

@@ -975,8 +975,6 @@ module EE
     # If the project is inside a fork network, the mirror URL must
     # also belong to a member of that fork network
     def import_url_inside_fork_network
-      return unless ::Feature.enabled?(:block_external_fork_network_mirrors, self, default_enabled: :yaml)
-
       if forked?
         mirror_project = ::Project.find_by_url(import_url)
 

ee/spec/models/project_spec.rb

@@ -2709,15 +2709,6 @@ RSpec.describe Project do
         stub_config_setting(host: 'gitlab.com')
       end
 
-      context 'feature flag is disabled' do
-        before do
-          stub_feature_flags(block_external_fork_network_mirrors: false)
-          project.import_url = "https://customgitlab.com/foo/bar.git"
-        end
-
-        it { is_expected.to be_valid }
-      end
-
       context 'the project is the root of the fork network' do
         before do
           project.import_url = "https://customgitlab.com/foo/bar.git"