tests: add supplementalGroups to pod-number-cpu for guest-pull

The genpolicy guest-pull check now fails closed when an image carries
supplemental groups that containerd won't reproduce while pulling the
layers inside the guest, and quay.io/prometheus/busybox:latest happens
to ship gid 10 (wheel).  pod-number-cpu.yaml was simply missed when the
other busybox manifests got their securityContext, so genpolicy bails
out on the expected/actual gid mismatch.

Let's declare supplementalGroups: [10] explicitly, just like we already
do for the other busybox-based pods, so the generated policy lines up
with what containerd actually applies.

Signed-off-by: Fabiano Fidêncio <ffidencio@nvidia.com>
Assisted-by: Cursor <cursoragent@cursor.com>

tests/integration/kubernetes/runtimeclass_workloads/pod-number-cpu.yaml

@@ -9,6 +9,8 @@ metadata:
   name: cpu-test
 spec:
   runtimeClassName: kata
+  securityContext:
+    supplementalGroups: [10]
   containers:
   - name: c1
     image: quay.io/prometheus/busybox:latest