Update item-pipeline.rst

insert is deprecated, use insert_one instead.

docs/topics/item-pipeline.rst

@@ -156,7 +156,7 @@ method and how to clean up the resources properly.::
             self.client.close()
 
         def process_item(self, item, spider):
-            self.db[self.collection_name].insert(dict(item))
+            self.db[self.collection_name].insert_one(dict(item))
             return item
 
 .. _MongoDB: https://www.mongodb.org/