ci/zink: Enable the validation layer on the TGL GL46 run.

We recently had an issue where an anv merge failed due to a bug in zink, which validation would have caught. Get some coverage by default on the main branch.

This increases runtime from 10:45 to 12:50. I don't feel good about this, but I've got !22451 (merged) and https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/4398 in flight to try to knock the time back down.