Update get_json function call for werkzeug 2.1.0+ (#1939)

Co-authored-by: Anton Pirker <[email protected]>

Author: michielderoos

sentry_sdk/integrations/flask.py

@@ -173,7 +173,7 @@ def is_json(self):
 
     def json(self):
         # type: () -> Any
-        return self.request.get_json()
+        return self.request.get_json(silent=True)
 
     def size_of_file(self, file):
         # type: (FileStorage) -> int