add kustomize image tag v5.6.0

Author: koba1t

registry.k8s.io/images/k8s-staging-kustomize/images.yaml

@@ -43,3 +43,4 @@
     "sha256:7492c35d6fbe64e05100009915167a37b285ca7391067fa0c7bec9a7d1856882": ["v5.4.1" ]
     "sha256:df5202136d4837f7ec0d1a8f5666acd3d0798825559c7dfde785fef0f5af9690": ["v5.4.2" ]
     "sha256:6dd0a67e2a8634a5d1aabd9c5e888ff220663e979b55bc17fe4b3a845718bb10": ["v5.4.3" ]
+    "sha256:b5f56e6becd1ba93a1a775a149763e3841a177beb10191624100bed81b44d297": ["v5.6.0" ]