chore(deps): update helm release gateway to v1.21.1

Author: renovate[bot]

apps/istio-ingress/base/kustomization.yaml

@@ -4,7 +4,7 @@ namespace: istio-system
 helmCharts:
   - name: gateway
     releaseName: gateway
-    version: 1.18.0
+    version: 1.21.1
     repo: https://istio-release.storage.googleapis.com/charts
     valuesInline:
       name: istio-ingressgateway