PYTHON-1362 - Useless check in aggregate_raw_batches

The method had checked whether any SON manipulators were configured, and
raised an error if so. But users should understand that SON manipulators
can't affect raw batches, and checking for them raises a deprecation
warning.

pymongo/command_cursor.py

@@ -206,10 +206,6 @@ class CommandCursor(object):
 
         return len(self.__data)
 
-    @property
-    def _collection(self):
-        return self.__collection
-
     @property
     def alive(self):
         """Does this cursor have the potential to return more data?
@@ -276,11 +272,6 @@ class RawBatchCommandCursor(CommandCursor):
         super(RawBatchCommandCursor, self).__init__(
             collection, cursor_info, address, retrieved)
 
-        db = self._collection.database
-        if db.outgoing_manipulators or db.outgoing_copying_manipulators:
-            raise InvalidOperation("Raw batches are not compatible with"
-                                   " SON manipulators.")
-
     def _unpack_response(self, response, cursor_id, codec_options):
         return helpers._raw_response(response, cursor_id)