Fix regression introduced by b9d6b628a9

When calculated the palette height based in the size of children,
forgoten add the border size. That moved the palette in the device icons
4 pixels to the bottom, then the gap was miscalcuated and the border
button border was not draw.

Signed-off-by: Gonzalo Odiard <godiard@sugarlabs.org>

src/sugar3/graphics/palettewindow.py

@@ -626,6 +626,10 @@ class PaletteWindow(GObject.GObject):
         for child in self._widget.get_children():
             child_req = child.size_request()
             total_height += child_req.height
+
+        # need add the border line width as defined in sugar-artwork
+        line_width = 2
+        total_height += line_width * 2
         req.height = total_height
 
         position = invoker.get_position_for_alignment(self._alignment, req)