Delete lm_eval/tasks/glue/sst directory

lm_eval/tasks/glue/sst/default.yaml

-group: glue
-task: sst
-dataset_path: glue
-dataset_name: sst
-output_type: multiple_choice
-training_split: train
-validation_split: validation
-doc_to_text: "{{sentence}}\nQuestion: Is this sentence positive or negative?\nAnswer:"
-doc_to_target: label
-doc_to_choice: ["negative", "positive"]
-metric_list:
-  - metric: acc
-metadata:
-  - version: 1.0