update helm charts

This MR updates the theodolite role-binding from API version rbac.authorization.k8s.io/v1beta1 to rbac.authorization.k8s.io/v1 and updates the Helm charts of Prometheus, Grafana and Lag-Exporter.

Closes #260 (closed) Closes #251 (closed)

helm/templates/theodolite/role-binding.yaml

 {{- if .Values.rbac.create -}}
-apiVersion: rbac.authorization.k8s.io/v1beta1
+apiVersion: rbac.authorization.k8s.io/v1
 kind: RoleBinding
 metadata:
   name:  {{ include "theodolite.fullname" . }}