ci: update helm chart testing workflow

[afdesk]

Description

This PR updates Helm Chart testing workflow to follow the docs of https://github.com/helm/chart-testing-action

Checklist

• I've read the guidelines for contributing to this repository.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).