cleanup: Avoid unnecessary braces

Our coding style has always been to avoid braces when all blocks
are single-lines.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/805

js/ui/status/volume.js

@@ -59,9 +59,8 @@ var StreamSlider = class {
     }
 
     set stream(stream) {
-        if (this._stream) {
+        if (this._stream)
             this._disconnectStream(this._stream);
-        }
 
         this._stream = stream;