Do not override ActiveRecord associations to mark and allow cross-joins

What does this MR do and why?

See description of #424307 (closed) for details.

We need to change 2 problematic instances of allowing cross-joins to the safer option, which is what this MR does.

Doing this leads to an N+1 check spec failing, and that spec has been skipped for now. A followup issue has been created to make sure it is worked on later.

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Related to #424307 (closed)