src/update_handler: remove debug message in vfat_label_generator
src/update_handler: remove debug message in vfat_label_generator

Previously, this printed each invalid character one-by-one during checking.
As this is derived from the slot name, we don't need to complain about invalid
characters.

Signed-off-by: Jan Luebbe <3a82f1ac4ad59607a20f180f1c67ac8ba31ad0d5@pengutronix.de>

jluebbe/rauc,jluebbe/rauc,jluebbe/rauc,rauc/rauc,rauc/rauc,ejoerns/rauc,ejoerns/rauc,rauc/rauc,ejoerns/rauc