fix(MetricsControl.test): add missing datasource prop

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

superset-frontend/src/explore/components/controls/MetricControl/MetricsControl.test.tsx

@@ -51,6 +51,7 @@ const defaultProps = {
     { metric_name: 'sum__value', expression: 'SUM(energy_usage.value)' },
     { metric_name: 'avg__value', expression: 'AVG(energy_usage.value)' },
   ],
+  datasource: undefined,
   datasourceType: 'sqla',
 };