Follow-up from "Update merge request widget serializers"

The following discussion from !180999 (merged) should be addressed:

• @jwoodwardgl started a discussion: (+8 comments)

  One of the tests is flaky. I noticed this when I ran it too. I’m not sure why. I will take a look tomorrow. If I don’t figure it out when you’re online we can definitely do some pairing

  rspec --seed 28645 ee/spec/serializers/ee/merge_request_poll_widget_entity_spec.rb fails consistently

  If I don't use let_it_be it works fine. I am going to push and create a follow-up to improve the spec.

I'm going to mark this as a spike as it's not clear why this test is not working when using let_it_be. It's order dependent but not obvious why.

The fix is https://gitlab.com/gitlab-org/gitlab/-/merge_requests/180999/diffs?diff_id=1265453621&start_sha=11e2c981ac0ae73a7fa0efbbd2e0c741ab9d2a1d

Reversing this change and using the seed 28645 should surface the error again

Priority is pretty low on this as it's not affecting the app, just the test suite.