API v1 is compatible with helm v2 and v2 is not.
However, helm v2 (the Tiller deployment mechanism) was deprecated in 2020
and no-one should be using it anymore.
This PR also adds a CI lint test for helm chart
Updates tailscale/tailscale#9222
Signed-off-by: Irbe Krumina <irbe@tailscale.com>