fix: pymongo requires pymongo.collection import (#28)

The latest version of pymongo (4.9.1) doesn't define `pymongo.collection`
unless you import it explicitly. edx-platform uses an older pymongo (4.4.0)
which is compatible whether or not you import `pymongo.collection`
explicitly.

Author: jikamens

mongodb_proxy.py

@@ -17,6 +17,7 @@
 from functools import wraps
 import logging
 import pymongo
+import pymongo.collection
 import time
 
 log = logging.getLogger(__name__)