Add jest unit for approval rules
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The following discussion from !47475 should be addressed:
- [ ] @mlunoe started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/47475#note_455035511): (+1 comment)
> **Thought**: I was wondering why you were implementing this as rspec over jest unit tests and diving into it a bit more, I believe the answer is that there was already an rspec pattern in place. Since we are migrating this to be Vue I think it would make sense to start thinking about moving these tests to jest. This could be done in a follow-up issue/MR.
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