custom performance metrics - removing reference to previously deleted…

… validation function (#1391)

## Description

Bug fix: removing reference to `_validate_org_and_dataset` in
`tag_custom_performance_metric`, which was removed in
#1311.

- [x] I have reviewed the [Guidelines for Contributing](CONTRIBUTING.md)
and the [Code of Conduct](CODE_OF_CONDUCT.md).

Co-authored-by: felipe207 <felipe@whylabs.ai>

python/whylogs/api/writer/whylabs.py

@@ -430,7 +430,6 @@ def tag_custom_performance_column(
             column=column,
             default_metric=default_metric,
         )
-        self._validate_org_and_dataset()  # TODO this just doesn't exist?
         try:
             res = api_instance.put_entity_schema_metric(self._org_id, self._dataset_id, metric_schema)
             return True, str(res)