Test: quarantine scroll to discussion test

What does this MR do and why?

Quarantine flaky test as it has created two incidents in two days:

• gitlab-org/quality/engineering-productivity/master-broken-incidents#3489 (closed)
• gitlab-org/quality/engineering-productivity/master-broken-incidents#3468 (closed)

Failure issue: #410029

MR acceptance checklist

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