lab 3 / Add Purge step to be coherent

[pierre-yves-monnet]

To be consistent, a step "purge" should be added

Same as Lab 2

Delete Release

helm uninstall camunda-platform

kubectl delete pvc --all

k delete pod minio

[jonathanlukas]

Done with https://github.com/camunda-consulting/c8-devops-workshop/commit/a985900e974ba616607402e4975cb3cf436d8d63