Update sendAll and sendMulticast documentation to reflect json responses

Author: ZachOrr

firebase_admin/messaging.py

@@ -103,7 +103,7 @@ def sendAll(messages, dry_run=False, app=None):
         app: An App instance (optional).
 
     Returns:
-        list: A list of message ID string that uniquely identifies the sent the messages.
+        list: A list of dictionaries from json responses for each message sent.
 
     Raises:
         ApiCallError: If an error occurs while sending the message to FCM service.
@@ -124,7 +124,7 @@ def sendMulticast(tokens, message, dry_run=False, app=None):
         app: An App instance (optional).
 
     Returns:
-        list: A list of message ID string that uniquely identifies the sent the messages.
+        list: A list of dictionaries from json responses for each message sent.
 
     Raises:
         ApiCallError: If an error occurs while sending the message to FCM service.