Remove the push-down optimization restriction that was added by

Remove the push-down optimization restriction that was added by
check-in [1ad41840c5e0fa70] because it is no longer needed after
the enhancements to compound query processing in check-in [27655c9353620aa5]
This resolves the performance regression reported by
[forum:/forumpost/bcc4375032|forum post bcc4375032].

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