sudo: bump to version 1.8.23

Use += for the SUDO_CONF_ENV conditional assignment to avoid override of
SUDO_CONF_ENV assignments that might be added in the future.

Add license file hash.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>