Update _cot_fewshot_template_yaml

BBH cot fewshot already has fewshot examples in the description. So num_fewshot needs to be set to 0 so that users won't mistakenly set other num_fewshot values.

lm_eval/tasks/bbh/cot_fewshot/_cot_fewshot_template_yaml

@@ -24,5 +24,6 @@ filter_list:
       - function: "regex"
         regex_pattern: "(?<=the answer is )(.*)(?=.)"
       - function: "take_first"
+num_fewshot: 0
 metadata:
   - version: 0.0