Fix typo? (#17590)

Author: phenomnomnominal

src/youtube-player/README.md

@@ -39,7 +39,7 @@ export class YoutubePlayerExampleModule {
   selector: 'youtube-player-example',
 })
 class YoutubePlayerExample implements OnInit {
-  onInit() {
+  ngOnInit() {
     // This code loads the IFrame Player API code asynchronously, according to the instructions at
     // https://developers.google.com/youtube/iframe_api_reference#Getting_Started
     const tag = document.createElement('script');