need to allow force-retry on sylva-units HelmRelease

in !4252 (merged), merged last week, we addressed #1533 (closed), which we thought was wise to do because we had no case in mind where the installation of sylva-units would fail

but since this change I've seen failure where the sylva-units HelmRelease can't be updated because the rancher-webhook that is present on many core resources including Secrets and failurePolicy: Fail was broken

https://gitlab.com/sylva-projects/sylva-core/-/jobs/9961920690:

    conditions:
    - lastTransitionTime: "2025-05-07T13:57:41Z"
      message: Failed to upgrade after 1 attempt(s)
      observedGeneration: 2
      reason: RetriesExceeded
      status: "True"
      type: Stalled
    - lastTransitionTime: "2025-05-07T13:47:07Z"
      message: 'Helm upgrade failed for release sylva-system/sylva-units with chart
        sylva-units@0.0.0-git-1f9efe25+1: failed to create resource: Internal error
        occurred: failed calling webhook "rancher.cattle.io.secrets": failed to call
        webhook: Post "https://rancher-webhook.cattle-system.svc:443/v1/webhook/mutation/secrets?timeout=15s":
        dial tcp 100.73.92.70:443: connect: connection refused'

💡 Short summary: I think we need to revert !4252 (merged)

(even if this failure is apparently not frequent)