Change the parameter immediate of send_device_messages to default to True

changelog.d/15297.bugfix

@@ -0,0 +1 @@
+Fix a bug introduced in Synapse v1.55.0 which could cause a delay in sending to-device messages.

synapse/federation/sender/__init__.py

@@ -783,7 +783,7 @@ def send_edu(self, edu: Edu, key: Optional[Hashable]) -> None:
         else:
             queue.send_edu(edu)
 
-    def send_device_messages(self, destination: str, immediate: bool = False) -> None:
+    def send_device_messages(self, destination: str, immediate: bool = True) -> None:
         if destination == self.server_name:
             logger.warning("Not sending device update to ourselves")
             return