fixed typo

Author: parambole

MaxText/tests/multi_token_prediction_test.py

@@ -139,7 +139,7 @@ def __call__(
     return self.mtp_block(
         main_hidden_state,
         self.shared_embedding,
-        self.self.output_head,
+        self.output_head,
         input_ids,
         target_ids,
         target_mask,