Sure, if you grab the source package (`apt-get source compiz`) and edit the debian/patches/series file to comment out 015_draw_dock_shadows_on_desktop.patch then build the package (`debuild binary`) you'll end up with a package that doesn't have this feature. You'll want to raise the ubuntu version in debian/changelog though so the archive version doesn't upgrade over yours.
Sure, if you grab the source package (`apt-get source compiz`) and edit the debian/ patches/ series file to comment out 015_draw_ dock_shadows_ on_desktop. patch then build the package (`debuild binary`) you'll end up with a package that doesn't have this feature. You'll want to raise the ubuntu version in debian/changelog though so the archive version doesn't upgrade over yours.