PYTHON-1621 Modify change stream output example for manual (mongodb#370)

Author: prashantmital

test/test_examples.py

@@ -695,12 +695,8 @@ def insert_docs():
 
  # Start Changestream Example 4
  pipeline = [
- {"$match": {
- "$or": [
- {"fullDocument.username": "alice"},
- {"operationType": {"$in": ["delete"]}}]
- }
- }
+ {'$match': {'fullDocument.username': 'alice'}},
+ {'$addFields': {'newField': 'this is an added field!'}}
  ]
  cursor = db.inventory.watch(pipeline=pipeline)
  document = next(cursor)