Replace the 'project/merge_requests.feature' spinach test with an rspec analog

Merged username-removed-86853 requested to merge replace_project_merge_requests.feature into master

What does this MR do?

Replaces the EE related spinach specs as part of

Why was this MR needed?

This is a part of the spinach removal campaign.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?