doc: typo: interal->internal.

Fixes a copy typo in the events.md docs.

PR-URL: #5849
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/events.markdown

@@ -402,14 +402,14 @@ myEmitter.on('event', callbackA);
 myEmitter.on('event', callbackB);
 
 // callbackA removes listener callbackB but it will still be called.
-// Interal listener array at time of emit [callbackA, callbackB]
+// Internal listener array at time of emit [callbackA, callbackB]
 myEmitter.emit('event');
   // Prints:
   //   A
   //   B
 
 // callbackB is now removed.
-// Interal listener array [callbackA]
+// Internal listener array [callbackA]
 myEmitter.emit('event');
   // Prints:
   //   A