Remove no longer needed test code

What does this MR do and why?

Remove no longer needed test code that was originally introduced in !62683 (merged) for online_garbage_collection_spec.rb E2E spec. The test was removed in !121388 (merged) but it appears some page objects still need to be cleaned up.

This came up as part of of gitlab-org/quality/quality-engineering/team-tasks#1825 (closed) refactor.

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