Add feature test for role promotion management `rejection` flow

What does this MR do and why?

This is a follow up from !171572 (merged). In the previous MR we added a test for the approval flow, and after this feedback we decided to create this MR to add a test for the rejection flow.

References

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• Issue: #462689 (closed)
• Previous MR: !171572 (merged)

MR acceptance checklist

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Screenshots or screen recordings

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How to set up and validate locally

bundle exec rspec ee/spec/features/users/role_promotion_spec.rb