Fix 1455: Protect from raw next() calls (#1456)

Author: lancetarn

instrumentation/opentelemetry-instrumentation-tornado/tests/test_metrics_instrumentation.py

@@ -57,7 +57,7 @@ def sorted_metrics(metrics):
     def assert_metric_expected(
         self, metric, expected_value, expected_attributes
     ):
-        data_point = next(metric.data.data_points)
+        data_point = next(iter(metric.data.data_points))
 
         if isinstance(data_point, HistogramDataPoint):
             self.assertEqual(
@@ -78,7 +78,7 @@ def assert_metric_expected(
     def assert_duration_metric_expected(
         self, metric, duration_estimated, expected_attributes
     ):
-        data_point = next(metric.data.data_points)
+        data_point = next(iter(metric.data.data_points))
 
         self.assertAlmostEqual(
             data_point.sum,