Document the support of the default CNI of GKE by Kuma CNI

[jijiechen]

Description

On GKE clusters, our docs says that the users must have network policy enabled to use Kuma CNI.

Page location: https://kuma.io/docs/2.9.x/production/dp-config/cni/#configure-the-kuma-cni

This is actually not requried according to a manual verification: the default CNI on GKE standard clusters have similar CNI configurations to other CNI implementations on GKE (Calico and Cilium), the only difference is file name of the conflist.

The default file name of the conflist is 10-containerd-net.conflist

@Icarus9913 and I have tested the following installation on a GKE standard cluster and Kuma CNI worked well and demo app pod ran successfully:

./kuma-2.9.0/bin/kumactl install control-plane \
  --set "kuma.cni.enabled=true" \
  --set "kuma.cni.chained=true" \
  --set "kuma.cni.netDir=/etc/cni/net.d" \
  --set "kuma.cni.binDir=/home/kubernetes/bin" \
  --set "kuma.cni.confName=10-containerd-net.conflist" \
  | kubectl apply -f -