cleanup: remove old adaptive simulcast config option

config.js

     disableStats: false,
     disableAudioLevels: false,
     channelLastN: -1, // The default value of the channel attribute last-n.
-    //disableAdaptiveSimulcast: false,
     enableRecording: false,
     enableWelcomePage: true,
     //enableClosePage: false, // enabling the close page will ignore the welcome