Let users use the other mouse button to switch

As users can have different primary mouse buttons (left vs right) it
might happen, that a user with a different
preference wants to switch. Currently they need
to use the mouse button, that the current
user prefers.

This change enables users to use either the left or right button.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1972>

js/ui/unlockDialog.js

@@ -579,6 +579,7 @@ var UnlockDialog = GObject.registerClass({
         this._otherUserButton = new St.Button({
             style_class: 'modal-dialog-button button switch-user-button',
             accessible_name: _('Log in as another user'),
+            button_mask: St.ButtonMask.ONE | St.ButtonMask.THREE,
             reactive: false,
             opacity: 0,
             x_align: Clutter.ActorAlign.END,