Remove without_project_namespaces scope on children

Children association already filters project namespaces

app/models/concerns/loaded_in_group_list.rb

@@ -69,7 +69,7 @@ module LoadedInGroupList
   end
 
   def subgroup_count
-    @subgroup_count ||= try(:preloaded_subgroup_count) || children.without_project_namespaces.count
+    @subgroup_count ||= try(:preloaded_subgroup_count) || children.count
   end
 
   def member_count

spec/models/concerns/loaded_in_group_list_spec.rb

@@ -25,7 +25,7 @@ RSpec.describe LoadedInGroupList do
     context 'with project namespaces' do
       let_it_be(:group1) { create(:group, parent: parent) }
       let_it_be(:group2) { create(:group, parent: parent) }
-      let_it_be(:project_namespace) { create(:project_namespace, project: project) }
+      let_it_be(:project_namespace) { project.project_namespace }
 
       it 'does not include project_namespaces in the count of subgroups' do
         expect(found_group.preloaded_subgroup_count).to eq(3)

spec/services/groups/transfer_service_spec.rb

@@ -253,14 +253,18 @@ RSpec.describe Groups::TransferService, :sidekiq_inline do
           expect(transfer_service.error).to eq('Transfer failed: The parent group already has a subgroup or a project with the same path.')
         end
 
-        context 'with project namespace' do
+        # currently when a project is created it gets a corresponding project namespace
+        # so we test the case where a project without a project namespace is transferred
+        # for backward compatibility
+        context 'without project namespace' do
           before do
             project_namespace = project.project_namespace
-            project.update!(project_namespace_id: nil)
-            project_namespace.destroy!
+            project.update_column(:project_namespace_id, nil)
+            project_namespace.delete
           end
 
           it 'adds an error on group' do
+            expect(project.reload.project_namespace).to be_nil
             expect(transfer_service.execute(new_parent_group)).to be_falsy
             expect(transfer_service.error).to eq('Transfer failed: Validation failed: Group URL has already been taken')
           end