fix(k8up): switch to Kustomize

Helm doesn't include CRDs

system/k8up-operator/Chart.yaml

@@ -1,7 +0,0 @@
-apiVersion: v2
-name: k8up
-version: 0.0.0
-dependencies:
-  - name: k8up
-    version: 2.0.2
-    repository: https://charts.appuio.ch

system/k8up-operator/kustomization.yaml

@@ -0,0 +1,7 @@
+# TODO switch back to Helm when they include CRDs
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - github.com/k8up-io/k8up/config/default?ref=master
+  - schedule.yaml