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>
Thomas Petazzoni