refactor Unmarshal Kustomization struct code

api/krusty/namespacedgenerators_test.go

@@ -12,8 +12,6 @@ import (
 func TestNamespacedGenerator(t *testing.T) {
 	th := kusttest_test.MakeHarness(t)
 	th.WriteK(".", `
-apiVersion: kustomize.config.k8s.io/v1beta1
-kind: Kustomization
 configMapGenerator:
 - name: the-non-default-namespace-map
   namespace: non-default