add target delimiter

lm_eval/tasks/ai2d/ai2d.yaml

@@ -4,6 +4,7 @@ output_type: multiple_choice
 test_split: test
 doc_to_text: "<image> Question: {{question}}\nAnswer:"
 doc_to_target: "{{ answer | int }}"
+target_delimiter: ""
 doc_to_choice: options
 doc_to_image:
   - image