refactor: remove unnecessary try-except in _should_validate_notification

The try-except block was unnecessary since getattr already handles
the case where the attribute doesn't exist by returning None.

Author: donghao1393

src/mcp/shared/session.py

@@ -294,13 +294,10 @@ def _should_validate_notification(self, message_root: JSONRPCNotification) -> bo
         Determines if a notification should be validated.
         Internal notifications (like notifications/cancelled) should be ignored.
         """
-        try:
-            return (
-                getattr(message_root, "method", None) != "notifications/cancelled" and
-                not self._closed
-            )
-        except:
-            return False
+        return (
+            getattr(message_root, "method", None) != "notifications/cancelled" and
+            not self._closed
+        )
 
     async def _receive_loop(self) -> None:
         async with (