Remove namespace from k8s event exporter kustomization

[dmsolr]

Now, k8s-event-exporter's kustomization managed namespace resource. using kustomize build ./release | kubectl delete -f - to deployment will delete the namespace within all resources If users deployed it in their namespace.

That sounds not good. So I propose that we don't manage the namespace. If the namespace does not exist, give a tip for the user on how to create a namespace.

[kezhenxu94]

Good idea, are you going to open a pull request?