typo fix

dekstopAudioStream --> desktopAudioStream

conference.js

                 = this._turnScreenSharingOff.bind(this, didHaveVideo);
 
             const desktopVideoStream = desktopStreams.find(stream => stream.getType() === MEDIA_TYPE.VIDEO);
-            const dekstopAudioStream = desktopStreams.find(stream => stream.getType() === MEDIA_TYPE.AUDIO);
+            const desktopAudioStream = desktopStreams.find(stream => stream.getType() === MEDIA_TYPE.AUDIO);
 
-            if (dekstopAudioStream) {
-                dekstopAudioStream.on(
+            if (desktopAudioStream) {
+                desktopAudioStream.on(
                     JitsiTrackEvents.LOCAL_TRACK_STOPPED,
                     () => {
                         logger.debug(`Local screensharing audio track stopped. ${this.isSharingScreen}`);