replace with no_train mmlu dataset

lm_eval/tasks/mmlu/default/_default_template_yaml

 group: mmlu
-dataset_path: cais/mmlu
+dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 test_split: test
 fewshot_split: dev
 fewshot_config:

lm_eval/tasks/mmlu/flan_cot_fewshot/_mmlu_flan_cot_fewshot_template_yaml

 group: mmlu_flan_cot_fewshot
-dataset_path: cais/mmlu
+dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 validation_split: validation
 fewshot_split: dev
 output_type: generate_until

lm_eval/tasks/mmlu/flan_cot_zeroshot/_mmlu_flan_generative_template_yaml

 group: mmlu_flan_cot_zeroshot
-dataset_path: cais/mmlu
+dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 validation_split: validation
 fewshot_split: dev
 output_type: generate_until

lm_eval/tasks/mmlu/flan_n_shot/_mmlu_flan_generative_template_yaml

 group: mmlu_flan_n_shot_generative
-dataset_path: cais/mmlu
+dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 test_split: test
 fewshot_split: dev
 output_type: generate_until

lm_eval/tasks/mmlu/flan_n_shot/_mmlu_flan_loglikelihood_template_yaml

 group: mmlu_flan_n_shot_loglikelihood
-dataset_path: cais/mmlu
+dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 test_split: test
 fewshot_split: dev
 output_type: multiple_choice