Possible fix for flaky sidebar specs

In both EE and FOSS specs, two labels are clicked in quick succession.
When the test fails, it appears that the first label was never actually
clicked.

To prevent some timing issue, we now pause after the first click to
verify the right number of active labels are present in the dropdown.

Closes https://gitlab.com/gitlab-org/gitlab/issues/118659

ee/spec/features/boards/sidebar_spec.rb

@@ -271,6 +271,7 @@ describe 'Issue Boards', :js do
         wait_for_requests
 
         click_link scoped_label_1.title
+        within('.dropdown-menu-labels') { expect(page).to have_selector('.is-active', count: 2) }
         click_link scoped_label_2.title
 
         wait_for_requests

spec/features/boards/sidebar_spec.rb

@@ -318,6 +318,7 @@ describe 'Issue Boards', :js do
         wait_for_requests
 
         click_link bug.title
+        within('.dropdown-menu-labels') { expect(page).to have_selector('.is-active', count: 3) }
         click_link regression.title
 
         wait_for_requests