Disable transaction checks for threaded spec

This test creates two threads to simulate a race condition, but the
transaction detection isn't thread safe so it picks up transactions from
the other thread.

Since the transaction check doesn't work properly in this test, we
disable it to work around the problem.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/295474

spec/features/merge_request/user_sees_pipelines_spec.rb

@@ -238,11 +238,15 @@ RSpec.describe 'Merge request > User sees pipelines', :js do
         threads = []
 
         threads << Thread.new do
-          @merge_request = MergeRequests::CreateService.new(project, user, merge_request_params).execute
+          Sidekiq::Worker.skipping_transaction_check do
+            @merge_request = MergeRequests::CreateService.new(project, user, merge_request_params).execute
+          end
         end
 
         threads << Thread.new do
-          @pipeline = Ci::CreatePipelineService.new(project, user, build_push_data).execute(:push)
+          Sidekiq::Worker.skipping_transaction_check do
+            @pipeline = Ci::CreatePipelineService.new(project, user, build_push_data).execute(:push)
+          end
         end
 
         threads.each { |thr| thr.join }