package/empty: bump to version 0.6.23d

Update hash of COPYRIGHT (update in year with
https://sourceforge.net/p/empty/code/ci/bb26b085df1285570c386d2aa9f5e3bf2fb92ec5/)

Release notes:
https://sourceforge.net/p/empty/code/ci/master/tree/CHANGELOG



Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>