Ignore customer sync for project namespaces

Project namespace will exist for each project, so probably no need
to sync these as other namespaces.

ee/app/models/ee/namespace.rb

@@ -105,7 +105,7 @@ module EE
       # Changing the plan or other details may invalidate this cache
       before_save :clear_feature_available_cache
 
-      after_commit :sync_name_with_customers_dot, on: :update, if: -> { name_previously_changed? }
+      after_commit :sync_name_with_customers_dot, on: :update, if: -> { name_previously_changed? && !project_namespace? }
     end
 
     # Only groups can be marked for deletion

ee/spec/models/ee/namespace_spec.rb

@@ -391,6 +391,12 @@ RSpec.describe Namespace do
         include_examples 'no sync'
       end
 
+      context 'when project namespace' do
+        let(:namespace) { create(:project_namespace) }
+
+        include_examples 'no sync'
+      end
+
       it 'triggers a name sync with CustomersDot' do
         expect(::Namespaces::SyncNamespaceNameWorker).to receive(:perform_async)
           .with(namespace.id).once