monoblue: remove unused elements and related css Since 91b0ada2d94b and c9b88695d894, when monoblue was introduced, the code this patch removes was untouched. Presumably, there supposed to be nice graphics in the screen corners, but there never were due to: - the css being commented out - ids of the elements and of the css selectors being different - and the png files absent The "corner" elements were unstyled and didn't affect the rest of the page, so I think it's safe to remove all this.