HTTP2 of CLI casued Timeout

[senayuki]

Summary

Argocli uses HTTP2, but the documentation does not mention this.

Motivation

I tried to follow the Getting Started docs to install and config ArgoCD. I accessed it through ingress-nginx and apisix, and the WebUI looked very normal. However, argocli login kept timing out.
I searched for some examples, and most users used port forward, but I tried to completely solve it.
Finally, I found that argocli uses HTTP2, which is not emphasized in the documentation. This has caused serious compatibility issues. After enabling HTTP2 on Apisix, the issue was resolved.

Proposal

I think the Getting Started document should emphasize the need for CLI to use HTTP2. And I also saw #20639, I haven't explore how CLI handles connections yet, maybe this PR will change everything.