remove Get started about Helm 2

[ydFu]

What this PR does / why we need it:

Remove about Helm v2 in README.md due to Helm v2 Deprecation.
After November 13, 2020,No further Helm v2 releases.

ref. helm-v2-deprecation-timeline

[CLAassistant]

All committers have signed the CLA.

[mflendrich]

I think it's the right thing to do; I was wondering about leaving Helm 2 as explicitly deprecated, but it's not a strong opinion.

To make a consistent change. Would you please send a matching PR for https://github.com/Kong/docs.konghq.com/tree/master/app/kubernetes-ingress-controller/1.1.x/deployment/ ?

Setting the "do not merge" label - so that we apply changes both here and to the docs repo simultaneously.

This change looks fine to go to main as opposed to next because Helm 2 is effectively EOL already.

[ydFu]

@mflendrich
Thanks for your suggestion,it is gains for me.
Send a matching PR to PR in Kong/docs.konghq.com.
I guess they are separate repositorys. Can be handled separately.

[mflendrich]

To be merged when Kong/docs.konghq.com#2524 is merged.