Fix pipeline 890867

What does this MR do and why?

Fix pipeline #890944:

• https://jihulab.com/gitlab-cn/gitlab/-/jobs/6024756 This is flaky case, test can pass locally.

Screenshots or screen recordings

How to set up and validate locally

bundle exec rspec spec/features/broadcast_messages_spec.rb

You will see:

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.