Fixed transient failure related to dropdown animations

spec/features/merge_requests/create_new_mr_spec.rb

@@ -20,6 +20,7 @@ feature 'Create New Merge Request', feature: true, js: true do
     expect(page).to have_content('Target branch')
 
     first('.js-source-branch').click
+    first('.dropdown-source-branch .dropdown-content')
     find('.dropdown-source-branch .dropdown-content a', match: :first).click
 
     expect(page).to have_content "b83d6e3"