ActivityButton: set the toggle_palette option to True

Setting this option will popup the Palette on left click or tap
and popdown the Palette if it is up. This functionality has been
added with c4165967d5e05607db8b3e0969b516da87855431.

Signed-off-by: Simon Schampijer <simon@laptop.org>
Acked-by: Manuel Quiñones <manuq@laptop.org>

src/sugar3/activity/widgets.py

@@ -60,6 +60,8 @@ class ActivityButton(ToolButton):
         self.set_icon_widget(icon)
         icon.show()
 
+        self.props.hide_tooltip_on_click = False
+        self.palette_invoker.props.toggle_palette = True
         self.props.tooltip = activity.metadata['title']
         activity.metadata.connect('updated', self.__jobject_updated_cb)