E2E test: update MWPS to use auto-merge

What does this MR do and why?

This E2E test is quarantined, and due to this it has fallen out of date and breaks because it is currently creating a project rather than an mr. This MR fixes the test and updates it to reflect Set to auto-merge rather than MWPS. The test passes locally.

More thorough testing is required before this test is de-quarantined.

How to set up and validate locally

QA_LOG_LEVEL=DEBUG QA_GITLAB_URL=http://192.168.4.31:3000  bundle exec rspec qa/specs/features/browser_ui/3_create/merge_request/merge_when_pipeline_succeeds_spec.rb --tag quarantine