Remove solo pack benchmark/USACO (kept team contests only)

benchmark/USACO/README.md

@@ -1,23 +0,0 @@
----
-dataset_info:
-  features:
-  - name: id
-    dtype: string
-  - name: difficulty
-    dtype: string
-  - name: input_output
-    dtype: string
-  - name: question
-    dtype: string
-  splits:
-  - name: test
-    num_bytes: 5907276795
-    num_examples: 520
-  download_size: 3800306899
-  dataset_size: 5907276795
-configs:
-- config_name: default
-  data_files:
-  - split: test
-    path: data/test-*
----