DOCSP-22799 updated monitoring example (#324)

* updated monitoring example

Author: kyuan-mongodb

source/code-snippets/monitoring/apm-subscribe.js

@@ -5,7 +5,7 @@ const { MongoClient } = require("mongodb");
 const uri =
   "mongodb+srv://<clusterUrl>/?replicaSet=rs&writeConcern=majority";
 
-const client = new MongoClient(uri);
+const client = new MongoClient(uri, { monitorCommands:true });
 
 // Replace <event name> with the name of the event you are subscribing to.
 const eventName = "<event name>";

source/fundamentals/monitoring/command-monitoring.txt

@@ -30,6 +30,12 @@ events created by the MongoDB deployment:
 .. literalinclude:: /code-snippets/monitoring/apm-subscribe.js
    :language: javascript
 
+.. note::
+
+   Command monitoring is disabled by default. To enable command
+   monitoring, pass the ``monitorCommands`` option as ``true`` to
+   your ``MongoClient`` constructor. 
+
 Event Descriptions
 ------------------