test(datastore): explicitly disable built-in metrics export in IT test

Author: lqiu96

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

@@ -157,7 +157,7 @@ public void setUp() {
                 DatastoreOpenTelemetryOptions.newBuilder()
                     .setMetricsEnabled(true)
                     .setOpenTelemetry(customOtel)
-                    .setExportBuiltinMetricsToGoogleCloudMonitoring(true)
+                    .setExportBuiltinMetricsToGoogleCloudMonitoring(false)
                     .build());
 
     if (transportOptions instanceof GrpcTransportOptions) {