[v1.5.x] Update Helm to v4.2.0

[stefanprodan]

Moving off our Helm fork to bring Flux 2.8 back to upstream.

PS needs testing on real clusters before deciding to go with this.

[matheuscscp]

Release candidate:

image: ghcr.io/fluxcd/helm-controller
tag: rc-13aa3242
digest: sha256:c5119c4aac35cb086d10ca5eafa1fc534e99f86581632ee5a5d85e0250d7ea88

[matheuscscp]

I was able to force-reconcile all the 14 HelmReleases in an EKS cluster:

● All 14 HelmReleases on the staging cluster force-reconciled successfully — no failures.

  ┌──────────────────────────────────┬────────────┬──────────────────┐
  │           HelmRelease            │   Status   │      Reason      │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ apps/demo-app                    │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ backend/memcached                │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ backend/redis                    │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ cert-manager/cert-manager        │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ flux-system/flux-mcp-enterprise  │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ flux-system/flux-operator        │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ flux-system/flux-status-server   │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ frontend/podinfo                 │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ ingress/external-dns             │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ ingress/ingress-nginx            │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ monitoring/kube-prometheus-stack │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ monitoring/metrics-server        │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ sso/dex                          │ Ready=True │ UpgradeSucceeded │
  ├──────────────────────────────────┼────────────┼──────────────────┤
  │ sso/keycloak                     │ Ready=True │ UpgradeSucceeded │
  └──────────────────────────────────┴────────────┴──────────────────┘