Update CosmosClientMetricsQuickStartAsync.java

Author: TheovanKraay

src/main/java/com/azure/cosmos/examples/prometheus/async/CosmosClientMetricsQuickStartAsync.java

@@ -118,7 +118,7 @@ private void clientMetricsPrometheusDemo()  {
         // </PrometheusTargetServer>
 
         // <CosmosClient>
-        //  Create sync client
+        //  Create async client
         client = new CosmosClientBuilder()
             .endpoint(AccountSettings.HOST)
             .key(AccountSettings.MASTER_KEY)