Upgrade twilio package to version 6.19.1 (#17395) (#17424)

- Bump twilio requirement to latest 6.19.1 version

- The generic response type is gone in the latest
  versions of the twilio package. It appears we were
  generating an empty response just to get the empty
  xml body. TwilML is the new base class all responses
  inherit from. So I've switched the code over to using
  and empty TwilML object instead.

- The exception type was moved to a different location.

homeassistant/components/notify/twilio_call.py

@@ -42,7 +42,7 @@ class TwilioCallNotificationService(BaseNotificationService):
 
     def send_message(self, message="", **kwargs):
         """Call to specified target users."""
-        from twilio import TwilioRestException
+        from twilio.base.exceptions import TwilioRestException
 
         targets = kwargs.get(ATTR_TARGET)