revise mbpp prompt (#2645)

lm_eval/tasks/mbpp/mbpp.yaml

@@ -4,9 +4,9 @@ dataset_name: full
 unsafe_code: true
 output_type: generate_until
 test_split: test
-doc_to_text: "You are an expert Python programmer, and here is your task: {{text}} Your code should pass these tests:\n\n{{test_list[0]}}\n{{test_list[1]}}\n{{test_list[2]}}\n[BEGIN]"
+doc_to_text: "You are an expert Python programmer, and here is your task: {{text}} Your code should pass these tests:\n\n{{test_list[0]}}\n{{test_list[1]}}\n{{test_list[2]}}\n[BEGIN]\n"
 doc_to_target: "{% if is_fewshot is defined %}{{code}}\n[DONE]{% else %}{{test_list[0]}}\n{{test_list[1]}}\n{{test_list[2]}}{% endif %}"
-target_delimiter: "\n"
+target_delimiter: ""
 metric_list:
   - metric: !function utils.pass_at_1
     aggregation: mean