Remove manually added :rtl pseudo classes

To deal with different CSS in RTL locales, we used to manually add
an :rtl pseudo class to some actors. With automatically assigned
:ltr/:rtl selectors this is no longer necessary.

https://bugzilla.gnome.org/show_bug.cgi?id=643835

js/ui/dash.js

@@ -262,11 +262,6 @@ Dash.prototype = {
                                        clip_to_allocation: true });
         this._box._delegate = this;
 
-        // This will eventually be automatic, see
-        // https://bugzilla.gnome.org/show_bug.cgi?id=584662
-        if (St.Widget.get_default_direction () == St.TextDirection.RTL)
-            this._box.add_style_pseudo_class('rtl');
-
         this.actor = new St.Bin({ y_align: St.Align.START, child: this._box });
         this.actor.connect('notify::height', Lang.bind(this,
             function() {