message: [sql lab] visualization flow: fixing the groupby parameter
diff: @@ -146,7 +146,7 @@ class VisualizeModal extends React.PureComponent {
  formData.metric = mainMetric.name;
  }
  if (mainGroupBy) {
  - formData.groupby = mainGroupBy.name;
  + formData.groupby = [mainGroupBy.name];
  }
  window.open(getExploreUrl(formData));
  },
  