Duplicate key `checksum/config` breaks Flux 2

Flux 2 version 15 and higher use Kustomize 4, which fails on duplicate keys:

Last Helm logs:
  Normal  error  7m2s (x86 over 19h)  helm-controller  reconciliation failed: Helm install failed: error while running post render on files: map[string]interface {}(nil): yaml: unmarshal errors:
  line 27: mapping key "checksum/config" already defined at line 26

Remove the key duplication from templates/statefulset.yaml to fix this issue