NautilusSelectionCanvasItem lost a few properties that control the way
the selection rectangle is drawn, namely the color and
stippling-enabling ones, which results in different rendering of the
file outlines when dragging multiple of them. At the moment, the
outlines are styled according to GTK_STYLE_CLASS_RUBBERBAND, which gives
them solid blue-ish borders and a light blue background.

This commit removes the code that sets those properties.