* Update apiVersion of PDB to policy/v1
According to https://kubernetes.io/docs/reference/using-api/deprecation-guide/ we can start using `policy/v1` in Kubernetes `1.21.
Without that you can observe such things in logs:
```
client.go:209: [debug] checking 5 resources for changes
W0901 11:28:35.264440 91 warnings.go:70] policy/v1beta1 PodDisruptionBudget is deprecated in v1.21+, unavailable in v1.25+; use policy/v1 PodDisruptionBudget
W0901 11:28:35.269403 91 warnings.go:70] policy/v1beta1 PodDisruptionBudget is deprecated in v1.21+, unavailable in v1.25+; use policy/v1 PodDisruptionBudget
W0901 11:28:35.297605 91 warnings.go:70] policy/v1beta1 PodDisruptionBudget is deprecated in v1.21+, unavailable in v1.25+; use policy/v1 PodDisruptionBudget
```
* use common.capabilities.policy.apiVersion
* bump chart version to 0.2.8
