selftest: Add vulkan-demos to checkpkg exceptions

vulkan-demos has not had any releases.

(From OE-Core rev: 910c16ef8e36286ce3e83e3c259ff7ec027b39b1)

Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/files/distrodata/checkpkg_exceptions

@@ -19,6 +19,7 @@ squashfs-tools
 tcf-agent
 unzip
 update-rc.d
+vulkan-demos
 x264
 xcursor-transparent-theme
 xinetd