Fix inconsistent result after apply in SKE cluster node pool taint value (#606)

* fix: Inconsistent result after apply in taint value

* feat: Also add UseStateForUnknown

Author: joaopalet

stackit/internal/services/ske/cluster/resource.go

@@ -485,6 +485,10 @@ func (r *clusterResource) Schema(_ context.Context, _ resource.SchemaRequest, re
 									"value": schema.StringAttribute{
 										Description: "Taint value corresponding to the taint key.",
 										Optional:    true,
+										Computed:    true,
+										PlanModifiers: []planmodifier.String{
+											stringplanmodifier.UseStateForUnknown(),
+										},
 									},
 								},
 							},