simplify the root-dependency check to cope with suspended or failed Kustomizations

The root-dependency check uses kubectl wait --for condition=Ready=false, but this only succeeds (for a reason that I don't understand) if the status.observedGeneration matches metadata.generation... which won't be true for a Kustomization that is failed or suspended. As a result if a Kustomization is failed or suspended, the root-dependency Kustomization Job will always fail and prevent upgrades (which will in particular make fixes a failed Kustomization harder...).

This MR fixes that by removing the check on Ready=False, which after discussion does really not seem necessary.

/cc @feleouet