fix: fixes KeyError when running with stale topic dlq (#82512)

Author: lynnagara

src/sentry/consumers/dlq.py

@@ -113,7 +113,7 @@ def submit(self, message: Message[KafkaPayload]) -> None:
         # If we get a valid message for a partition later, don't emit a filtered message for it
         if self.offsets_to_forward:
             for partition in message.committable:
-                self.offsets_to_forward.pop(partition)
+                self.offsets_to_forward.pop(partition, None)
 
         self.next_step.submit(message)