scripts: Drop .binary and .chroot extensions

Once upon a time, when Apertis was still using live-build, scripts
had to indicate in their extension if they had to be run in the chroot
environment or outside of it.

With Debos this is no longer needed, so drop the weird extensions that
were cargo-culted in this repository. :)

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>