feat: enable s390x prometheus check (#1920)

As of version 2.15.2, there is no available container image for
s390x. However, version 2.25.2 does provide support for this
architecture. This update enables the checks to run on s390x.

Signed-off-by: Nestor Acuna Blanco <nestor.acuna@ibm.com>

tools/prom-rule-ci/verify-rules.go

@@ -8,7 +8,7 @@ import (
 	"github.com/kubevirt/cluster-network-addons-operator/pkg/monitoring/rules"
 )
 
-const promImage = "quay.io/prometheus/prometheus:v2.15.2"
+const promImage = "quay.io/prometheus/prometheus:v2.25.2"
 
 func main() {
 	if len(os.Args) != 4 {