added for seq2seq greedy_until test

lm_eval/tasks/super_glue/boolq/seq2seq.yaml

+group:
+  - super-glue-lm-eval-v1
+task: "boolq-seq2seq"
+dataset_path: super_glue
+dataset_name: boolq
+output_type: greedy_until
+training_split: train
+validation_split: validation
+doc_to_text: "{{passage}}\nQuestion: {{question}}\nAnswer:"
+doc_to_target: "{{answer_choices[label]}}"
+gold_alias: "{{label}}" # this will be cast to an int.
+template_aliases: "{% set answer_choices = ['no', 'yes'] %}"
+metric_list:
+  - metric: exact_match
+    aggregation: mean
+    higher_is_better: true
+    ignore_case: true
+    ignore_punctuation: true