Wait for requests before continuing

Otherwise async requests while logging in with admin mode will happen
while factory_bot fixtures are created, causing Rails to lock, and the
spec to hang.

See https://gitlab.com/gitlab-org/gitlab/-/issues/337039

spec/features/expand_collapse_diffs_spec.rb

@@ -13,6 +13,8 @@ RSpec.describe 'Expand and collapse diffs', :js do
     sign_in(admin)
     gitlab_enable_admin_mode_sign_in(admin)
 
+    wait_for_requests
+
     # Ensure that undiffable.md is in .gitattributes
     project.repository.copy_gitattributes(branch)
     visit project_commit_path(project, project.commit(branch))