Removed webkit flag as it is not used (polyfill handles the differences)

Author: pavle-goloskokovic

v3/src/sound/webaudio/WebAudioSoundManager.js

@@ -6,16 +6,6 @@ var SoundValueEvent = require('../SoundValueEvent');
 var WebAudioSoundManager = new Class({
     Extends: BaseSoundManager,
     initialize: function WebAudioSoundManager(game) {
-        /**
-         * Flag indicating if Web Audio implementation is webkit or standards based.
-         * There are certain cases where they have to be handled differently.
-         *
-         * https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API/Porting_webkitAudioContext_code_to_standards_based_AudioContext
-         *
-         * @private
-         * @property {boolean} webkit
-         */
-        this.webkit = !!window['webkitAudioContext'] && !window['AudioContext'];
         /**
          * The AudioContext being used for playback.
          *