Palettes: remove comment about deprecated API

We make use of this API in the shell and in the toolkit itself
and never removed those deprecated calls. Let's leave it like
this for now and remove the comment.

src/sugar3/graphics/palette.py

@@ -34,8 +34,6 @@ from sugar3.graphics.palettewindow import PaletteWindow, \
     _PaletteWindowWidget, _PaletteMenuWidget
 from sugar3.graphics.palettemenu import PaletteMenuItem
 
-# DEPRECATED
-# Import these for backwards compatibility
 from sugar3.graphics.palettewindow import MouseSpeedDetector, Invoker, \
         WidgetInvoker, CursorInvoker, ToolInvoker, CellRendererInvoker
 assert MouseSpeedDetector