gh-142403: Avoid leaking file descriptor in socket.py

Author: AZero13

Lib/socket.py

@@ -416,6 +416,7 @@ def _sendfile_zerocopy(self, zerocopy_func, giveup_exc_type, file,
                     total_sent += sent
             return total_sent
         finally:
+            selector.close()
             if total_sent > 0 and hasattr(file, 'seek'):
                 file.seek(offset)