lint: fix confluent subscriber decorator annotation (#2604)

Author: Lancetnik

faststream/confluent/broker/registrator.py

@@ -114,7 +114,7 @@ def subscriber(
         *topics: str,
         partitions: Sequence["TopicPartition"] = (),
         polling_interval: float = 0.1,
-        group_id: None = None,
+        group_id: str | None = None,
         group_instance_id: None = None,
         fetch_max_wait_ms: int = 500,
         fetch_max_bytes: int = 50 * 1024 * 1024,

tests/mypy/confluent.py

@@ -120,3 +120,8 @@ def check_subscriber_instance_type(
 KafkaRouter(routers=[KafkaRouter()])
 KafkaRouter().include_router(KafkaRouter())
 KafkaRouter().include_routers(KafkaRouter())
+
+
+@KafkaBroker().subscriber("mykey", group_id="my_group", batch=True)
+async def process_msgs() -> None:
+    pass