fix @types/video.js typo: requestFullScreen -> requestFullscreen

related #28476
reference: https://github.com/videojs/video.js/blob/master/src/js/player.js#L2408

types/video.js/index.d.ts

@@ -4364,7 +4364,7 @@ declare namespace videojs {
 		 *
 		 * @fires Player#fullscreenchange
 		 */
-		requestFullScreen(): Player;
+		requestFullscreen(): Player;
 
 		/**
 		 * Report user activity

types/video.js/video.js-tests.ts

@@ -57,7 +57,7 @@ videojs("example_video_1").ready(function() {
 
 	this.height(480);
 
-	this.requestFullScreen();
+	this.requestFullscreen();
 
 	testEvents(this);