message: [table editor] better table header for Metrics tab
diff: @@ -433,6 +433,11 @@ export class DatasourceEditor extends React.PureComponent {
  return (
  <CollectionTable
  tableColumns={['metric_name', 'verbose_name', 'expression']}
  + columnLabels={{
  + metric_name: t('Metric'),
  + verbose_name: t('Label'),
  + expression: t('SQL Expression'),
  + }}
  expandFieldset={
  <FormContainer>
  <Fieldset>
  