h3: Remove streams on StreamClosed

Author: G1gg1L3s

src/hypercorn/protocol/h3.py

@@ -86,7 +86,8 @@ async def stream_send(self, event: StreamEvent) -> None:
             self.connection.send_headers(event.stream_id, event.headers)
             await self.send()
         elif isinstance(event, StreamClosed):
-            pass  # ??
+            # Remove a stream when it's closed to avoid memory leaks
+            self.streams.pop(event.stream_id, None)
         elif isinstance(event, Request):
             await self._create_server_push(event.stream_id, event.raw_path, event.headers)