argocd: upgrade to v3.5.6

3.5 is tested on Kubernetes 1.32 to 1.36; 3.4 stops at 1.35. It renders Helm charts with Helm 4.2.1 instead of 3.19; rendering all thirteen Helm apps with both gave the same manifests apart from whitespace, comments and document order.

argocd/kustomization.yaml

@@ -6,7 +6,7 @@ namespace: argocd
 
 # additional resources like the route, certificate and secrets.
 resources:
-- https://raw.githubusercontent.com/argoproj/argo-cd/refs/tags/v3.4.12/manifests/install.yaml
+- https://raw.githubusercontent.com/argoproj/argo-cd/refs/tags/v3.5.6/manifests/install.yaml
 - certificate.yaml
 - httproute.yaml
 - oidc-secret.yaml