cleanup: Avoid unnecessary parentheses in arrow functions

Parentheses are only needed if there are zero or multiple arguments.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/731

js/ui/calendar.js

@@ -1073,7 +1073,7 @@ var CalendarMessageList = class CalendarMessageList {
         this._clearButton.set_x_align(Clutter.ActorAlign.END);
         this._clearButton.connect('clicked', () => {
             let sections = [...this._sections.keys()];
-            sections.forEach((s) => s.clear());
+            sections.forEach(s => s.clear());
         });
         box.add_actor(this._clearButton);