Impossible to deploy on Kubernetes < v1.22 due to a hard version constraint in Chart.yaml

[vpedosyuk]

Describe the bug
The README says:

Kubernetes 1.22+ - This is the earliest version of Kubernetes tested. It is possible that this chart works with earlier versions but it is untested.

However, in fact, it's impossible to run it on, let's say, Kubernetes v1.21 because there's an explicit version check:
https://github.com/hashicorp/vault-helm/blob/main/Chart.yaml#L8

Consequently, I get the following error:

dry-run upgrade for comparison failed: chart requires kubeVersion: >= 1.22.0-0 which is incompatible with Kubernetes v1.21.2

To Reproduce
Steps to reproduce the behavior:

1. Install an older chart on Kubernetes 1.21
2. Try upgrading to the latest chart version

Expected behavior
It's still possible to deploy the Helm chart on older Kubernetes versions but without any guarantees as stated in README.md

[tomhjp]

Thanks for raising this, I agree we should keep the hard requirement looser, so in #916 I've reverted the minimum required version back to 1.20, but as you say it is without testing guarantees.

[vpedosyuk]

@tomhjp, thanks, v1.20 would work perfectly fine for me