Remove undocumented device from pushrules (#14727)

* Remove undocumented device from pushrules

* Add changelog

* Update changelog.d/14727.misc

* Rename 14727.misc to 14727.bugfix

Co-authored-by: David Robertson <davidr@element.io>

changelog.d/14727.bugfix

+Remove the unspecced `device` field from `/pushrules` responses.

synapse/push/clientformat.py

@@ -26,10 +26,7 @@ def format_push_rules_for_user(
     """Converts a list of rawrules and a enabled map into nested dictionaries
     to match the Matrix client-server format for push rules"""
 
-    rules: Dict[str, Dict[str, List[Dict[str, Any]]]] = {
-        "global": {},
-        "device": {},
-    }
+    rules: Dict[str, Dict[str, List[Dict[str, Any]]]] = {"global": {}}
 
     rules["global"] = _add_empty_priority_class_arrays(rules["global"])