Do not use transactional tests for this feature spec

The setup for this spec relies on multiple threads,
but it hangs with transactional tests + decomposed databases.

We could re-initialize database load balancing to re-establish a correct
connection to prevent the hang, but now we cannot see the data we
previously created. So the solution is to not use transactional tests,
and rely on database cleaner's deletion strategy

spec/features/merge_request/user_sees_pipelines_spec.rb

@@ -232,7 +232,7 @@ RSpec.describe 'Merge request > User sees pipelines', :js do
       sign_in user
     end
 
-    context 'when pipeline and merge request were created simultaneously' do
+    context 'when pipeline and merge request were created simultaneously', :delete do
       before do
         stub_ci_pipeline_to_return_yaml_file