Reverts player changes introduced in MR!1291 breaking background playback (#1509)

MR !1397

changes/changelog.d/1509.bugfix

@@ -0,0 +1 @@
+Reverts changes that break mobile browser playback (#1509)

front/src/components/audio/Player.vue

@@ -604,11 +604,8 @@ export default {
     async loadSound (newValue, oldValue) {
       let trackData = newValue
       const oldSound = this.currentSound
-      // stop all other sounds!
-      // we do this here (before the track has loaded) to get a predictable
-      // song order.
-      Howler.stop()
       if (oldSound && trackData !== oldValue) {
+        oldSound.stop(this.soundId)
         this.soundId = null
       }
       if (!trackData) {