chore(deps): update dependency fluxcd/flux2 to v2.6.4

Author: renovate-bot

contrib/flux/flux2/kustomization.yaml

@@ -2,7 +2,7 @@
 apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
-  - github.com/fluxcd/flux2/manifests/install?ref=v2.4.0
+  - github.com/fluxcd/flux2/manifests/install?ref=v2.6.4
   - flux-kustomization.yaml
   - repository.yaml
 patches: