message: fix bool -> string in description
diff: @@ -238,7 +238,7 @@ TF_CAPI_EXPORT extern void TF_OpKernelConstruction_GetAttrBool(
  // attr_name, list_size, total_size)). *status is set to TF_OK.
  //
  // If the attribute could not be found or could not be interpreted as
  -// bool, *status is populated with an error.
  +// string, *status is populated with an error.
  TF_CAPI_EXPORT extern void TF_OpKernelConstruction_GetAttrString(
  TF_OpKernelConstruction* ctx, const char* attr_name, void* val,
  size_t max_length, TF_Status* status);
  