fix test

Author: blink1073

test/asynchronous/test_transactions.py

@@ -586,7 +586,7 @@ async def test_case_1(self):
         # Create a MongoClient running against a configured sharded/replica set/load balanced cluster.
         client = async_client_context.client
         coll = client[self.db.name].test
-        coll.delete_many({})
+        await coll.delete_many({})
         # Start a new session on the client.
         async with client.start_session() as s:
             # Start a transaction on the session.