chore: Update comments in the ITs

Author: lqiu96

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreImpl.java

@@ -186,7 +186,7 @@ public void close() throws Exception {
     } catch (Exception e) {
       logger.log(Level.WARNING, "Failed to close channels", e);
     }
-    // Flush and shut down the built-in OTel SDK if active; no-op for user-provided instances.
+    // Shut down the built-in OTel SDK as we manage its lifecycle
     if (builtInOpenTelemetry instanceof OpenTelemetrySdk) {
       try {
         ((OpenTelemetrySdk) builtInOpenTelemetry).close();

java-datastore/google-cloud-datastore/src/test/java/com/google/cloud/datastore/ITDatastoreBuiltInAndCustomMetrics.java

@@ -106,13 +106,8 @@ public void setUp() {
     OpenTelemetrySdk customOtel =
         OpenTelemetrySdk.builder().setMeterProvider(customMeterProvider).build();
 
-    // Configure the Datastore client with BOTH backends active:
-    //   1. Built-in Cloud Monitoring export (enabled by default via
-    //      DatastoreOpenTelemetryOptions.exportBuiltinMetricsToGoogleCloudMonitoring = true)
-    //   2. User-configured OTel backend wired to the in-memory reader above.
-    //
-    // The resulting DatastoreMetricsRecorder will be a CompositeDatastoreMetricsRecorder that
-    // fans out all recording calls to both backends simultaneously.
+    // Do not enable setExportBuiltinMetricsToGoogleCloudMonitoring(false) for this IT
+    // as we will only rely on in-memory to collect the metrics for this test
     DatastoreOptions.Builder builder =
         DatastoreOptions.newBuilder()
             .setProjectId(PROJECT_ID)