package/ncftp: use correct SPDX license code

According to https://spdx.org/licenses/, the correct license code for
the "Clarified Artistic License" is ClArtistic.

The only other package in Buildroot containing code under this license
is google-breakpad, and it is already using the ClArtistic SPDX code.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
diff --git a/package/ncftp/ncftp.mk b/package/ncftp/ncftp.mk
index a3aa3fb..57c3a5d 100644
--- a/package/ncftp/ncftp.mk
+++ b/package/ncftp/ncftp.mk
@@ -8,7 +8,7 @@
 NCFTP_SOURCE = ncftp-$(NCFTP_VERSION)-src.tar.xz
 NCFTP_SITE = https://www.ncftp.com/public_ftp/ncftp
 NCFTP_TARGET_BINS = ncftp
-NCFTP_LICENSE = Clarified Artistic License
+NCFTP_LICENSE = ClArtistic
 NCFTP_LICENSE_FILES = doc/LICENSE.txt
 
 NCFTP_DEPENDENCIES = host-autoconf