ci: Reduce the size of the AKS VMs

We do **not** need a very powerful machine for our tests, as we're not
building anything there.

The instance we switched to (Standard_D2s_v5) still has nested virt
available, as shown here[0], but has half of the amount of vCPUs /
Memory, which should be fine only for running the tests, costing us
basically half of the price[1].

[0]:
https://learn.microsoft.com/en-us/azure/virtual-machines/dv5-dsv5-series
[1]:
https://azure.microsoft.com/en-us/pricing/details/virtual-machines/linux/#pricing

Fixes: #7955

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

tests/gha-run-k8s-common.sh

@@ -43,7 +43,7 @@ function create_cluster() {
     az aks create \
         -g "${AZ_RG}" \
         -n "$(_print_cluster_name ${test_type})" \
-        -s "Standard_D4s_v5" \
+        -s "Standard_D2s_v5" \
         --node-count 1 \
         --generate-ssh-keys \
         $([ "${KATA_HOST_OS}" = "cbl-mariner" ] && echo "--os-sku AzureLinux --workload-runtime KataMshvVmIsolation")