Fix CSS selector used in specs

This selector does not exist anymore so the spec fails

spec/features/projects_spec.rb

@@ -329,7 +329,7 @@
     it 'has working links to submodules' do
       click_link('645f6c4c')
 
-      expect(page).to have_selector('.qa-branches-select', text: '645f6c4c82fd3f5e06f67134450a570b795e55a6') # rubocop:disable QA/SelectorUsage
+      expect(page).to have_selector('[data-testid="branches-select"]', text: '645f6c4c82fd3f5e06f67134450a570b795e55a6')
     end
 
     context 'for signed commit on default branch', :js do