production: fix kustomization names

basic/clusters/production/namespace-kustomization.yaml

 apiVersion: kustomize.toolkit.fluxcd.io/v1beta1
 kind: Kustomization
 metadata:
-  name: stackspin-namespace
+  name: stackspout-namespace
   namespace: flux-system
 spec:
   interval: 30m

basic/clusters/production/sources-kustomization.yaml

 apiVersion: kustomize.toolkit.fluxcd.io/v1beta1
 kind: Kustomization
 metadata:
-  name: stackspin-sources
+  name: stackspout-sources
   namespace: flux-system
 spec:
   interval: 30m