Review solutions for `git_push` test triggering pipelines

After the great work by @niskhakova to add a git push test we unfortunately discovered that the test will then trigger pipelines en masse. This is problematic for several reasons:

• The current performance environments don't have runners so the queues just build and Sidekiq spins for ages
• On other environments (especially customers) that might lead to significant costs as many pipelines are triggered.

Task is to review options on how to prevent this while maintaining the test. Already tried disabling pipelines for the project but this then has the knock on effect of blocking api_v4_projects_pipelines.