fix test

re-worded an error message

Author: narsaynorath

tests/sentry/explore/endpoints/test_explore_saved_queries.py

@@ -1273,7 +1273,9 @@ def test_post_metrics_dataset_requires_metric_field(self) -> None:
                 },
             )
         assert response.status_code == 400, response.content
-        assert "Metric field is required for metrics dataset" in str(response.data)
+        assert "Metric field is required for non-equation queries on the metrics dataset" in str(
+            response.data
+        )
 
     def test_save_with_start_and_end_time(self) -> None:
         with self.feature(self.features):