Remove sidekiq check from "revert merge request" spec

What does this MR do and why?

In an attempt to get the spec at https://gitlab.com/gitlab-org/gitlab/-/blob/gmh-make-user-reverts-test-faster/spec/features/merge_request/user_reverts_merge_request_spec.rb#L32 to an acceptable time, this tries to remove the extra transaction checks for Sidekiq.

Related quarantine MR: Quarantine a flaky test (!164017 - closed) Related slowness report: [Test] spec/features/merge_request/user_reverts... (#454303)

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