Bump gitlab-experiment to 0.5.2 [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Bumping GLEX to get updated spec helpers and matcher that are more friendly when stubbing and expecting.

part of: #285286 gitlab-experiment#23

depends on: https://gitlab.com/gitlab-org/gitlab-experiment/-/merge_requests/90

Screenshots (strongly suggested)

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