gitlab-ci: enable building the test image for VK unconditionally

gitlab-ci: enable building the test image for VK unconditionally

It was diabled because RADV is the only driver that tests Vulkan
and running CTS on my personal machine and without recovery is
not safe enough for CI (too long and too unstable).

Now that we are going to test Fossilize with RADV, it's needed to
build the test image for VK unconditionally. As RADV now supports
creating NULL devices, the fossilize jobs can run everywhere.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3960>