doc: clarify this in event listeners

this === eventEmitter or this === instance of EventEmitter,
but it's this is not EventEmitter.

PR-URL: #20537
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>

doc/api/events.md

@@ -43,21 +43,21 @@ myEmitter.emit('event');
 ## Passing arguments and `this` to listeners
 
 The `eventEmitter.emit()` method allows an arbitrary set of arguments to be
-passed to the listener functions. It is important to keep in mind that when an
-ordinary listener function is called by the `EventEmitter`, the standard `this`
-keyword is intentionally set to reference the `EventEmitter` to which the
+passed to the listener functions. It is important to keep in mind that when
+an ordinary listener function is called, the standard `this` keyword
+is intentionally set to reference the `EventEmitter` instance to which the
 listener is attached.
 
 ```js
 const myEmitter = new MyEmitter();
 myEmitter.on('event', function(a, b) {
-  console.log(a, b, this);
+  console.log(a, b, this, this === myEmitter);
   // Prints:
   //   a b MyEmitter {
   //     domain: null,
   //     _events: { event: [Function] },
   //     _eventsCount: 1,
-  //     _maxListeners: undefined }
+  //     _maxListeners: undefined } true
 });
 myEmitter.emit('event', 'a', 'b');
 ```