fix: assert high-res metric value is present instead of summing

With the padded window, both standard (4) and high-res (8) product
metrics appear as separate 1-second buckets, so the sum is 12 not 8.
Instead, assert that the high-res value (8.0) is contained in the
returned data points.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phipag

powertools-e2e-tests/src/test/java/software/amazon/lambda/powertools/MetricsE2ET.java

@@ -123,9 +123,8 @@ void test_recordMetrics() {
                 paddedEnd, 1, NAMESPACE,
                 "products", Collections.singletonMap("Environment", "test"));
 
-        // With a period of 1 second, only the high resolution metric is available.
-        // Sum all data points as the padded window may return multiple 1-second buckets.
-        double highResSum = productMetricDataResult.stream().mapToDouble(Double::doubleValue).sum();
-        assertThat(highResSum).isEqualTo(8);
+        // With a period of 1 second and a padded window, both standard (4) and high resolution (8)
+        // metrics may appear as separate 1-second buckets. Verify the high resolution value is present.
+        assertThat(productMetricDataResult).contains(8.0);
     }
 }