radv/ci: reduce the parallelism for vkcts-vangogh

We are about to enable pre-merge testing for radv-zink on vangogh,
which would mean the steam decks would be used for the following jobs:

 * Mesa pre-merge CI:
  * zink: 3 (~12 minutes)
 * Mesa Post-merge CI:
   * vkcts: 4 (~30 minutes)
   * vkd3d: 1 (~5 minutes)
 * DXVK CI: 1 (takes ~4 hours)

This means we could have 9 jobs running at the same time on steam
decks, despite only having 6 available. By reducing the number of decks
allocated for VKCTS runs from 4 to 2, we get closer to the actual
availability, and since vkd3d is so short + DXVK CI runs so
infrequently, we should never have to wait for a deck for too long!

Unfortunately, with the change of parallelism, a known flake started
failing more consistently, so I added it to the flakes list.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Signed-off-by: Martin Roukala (né Peres) <martin.roukala@mupuf.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21873>

src/amd/ci/gitlab-ci.yml

@@ -375,7 +375,7 @@ vkcts-navi21-llvm-valve:
     RADV_DEBUG: llvm,checkir
 
 vkcts-vangogh-valve:
-  parallel: 4
+  parallel: 2
   extends:
     - .vkcts-test-valve
     - .vangogh-test-valve

src/amd/ci/radv-vangogh-aco-flakes.txt

@@ -1,3 +1,5 @@
+dEQP-VK.api.device_init.create_instance_device_intentional_alloc_fail.basic
+
 dEQP-VK.dynamic_rendering.basic.*
 
 # This fail is 100% reproducible when running vkcts in parallel mode,