overviewControls: Make sure dash is positioned at the bottom

We don't want the dash to expand, but if it's given more space
than requested, we want it to be positioned at the bottom.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1577>

js/ui/overviewControls.js

@@ -345,6 +345,7 @@ class DashFader extends FaderControl {
         super._init({
             x_expand: true,
             x_align: Clutter.ActorAlign.CENTER,
+            y_align: Clutter.ActorAlign.END,
         });
 
         this._dash = dash;