GetProcessSettings should not return volumeClaimTemplate for stateless processes

[johscheuer]

What would you like to be added/changed?

When a user calls spec.GetProcessSettings("stateless") the pod template will contain a volumeClaimTemplate which will be ignored in a later state (here: https://github.com/FoundationDB/fdb-kubernetes-operator/blob/main/internal/pod_models.go#L332-L345) I think it makes more sense to remove the volumeClaimTemplate directly in the spec.GetProcessSettings method to prevent confusion on the user side.