Follow-up to https://jira.mongodb.org/browse/SERVER-126176

FLE query analysis rejects any aggregate with a $changeStream stage under automatic encryption. This is to prevent forwarding the pipeline unanalyzed and sending encrypted fields to the server as plaintext.

A $changeStream pipeline whose subsequent stages do not reference any encrypted fields has no plaintext and is safe to allow. We should look into permitting the $changestreams for these cases