build-appliance-image: bump version to 14.0.0

Bumping to 14.0 was incorrect: upstream version tag is 14.0.0.
This change is done solely to improve accuracy of RRS version reporting.

(From OE-Core rev: ead744f0b8afd53b851128a89c14bb7025b339fb)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>