findByIdForStream redundant code and potential auth bypass

StreamDestinationFilterService.java:137-139:

public Optional findByIdForStream(String streamId, String id) {
collection.find(and(eq(FIELD_STREAM_ID, streamId), idEq(id)));
return utils.getById(id);
}

The collection.find(...) result is discarded — its return value is never consumed. The method then calls utils.getById(id) which ignores the streamId parameter entirely. If a caller assumes that the service will enforce access rights, it could result in an auth issue: a user who has access to stream A can look up a filter rule belonging to stream B as long as they know the rule's ID.

## Your Environment

* Graylog Version: 7.1