calcurse-caldav: Fix version check
calcurse-caldav: Fix version check

Since commit 41389ab (args.c: Revise help/usage/version output,
2016-01-28), the version string starts with "calcurse" (lowercase).

Signed-off-by: Lukas Fleischer <c9ca73f8336dcfb037ec2c2abf52d80a6847a5cd@calcurse.org>

lfos/calcurse,lfos/calcurse,lfos/calcurse