remove broken currentThread/setMuted mutation
remove broken currentThread/setMuted mutation

It tries to mutate a frozen object, which was introduced when we started freezing objects in vuex for performance reasons.

Despite this, the site worked fine for the user, because websocket updates did the job. I take this chance to remove the broken code, further embracing websockets for more essential page functionality.

yunity/foodsaving-frontend,yunity/karrot-frontend,yunity/foodsaving-frontend,yunity/foodsaving-frontend,yunity/karrot-frontend,yunity/foodsaving-frontend,yunity/karrot-frontend,yunity/karrot-frontend