Temp fix for mediaurl in create a message. (#537)

Co-authored-by: Nirav Nikhil <[email protected]>

Author: Devon-White

specs/compatibility-api/_spec_.yaml

@@ -7288,7 +7288,6 @@ paths:
                 - To
                 - From
                 - Body
-                - MediaUrl
               properties:
                 To:
                   type: string