docs: correct IPAM mode name in BGP control plane installation docs
docs: correct IPAM mode name in BGP control plane installation docs

The IPAM mode is currently called "cluster-pool-v2beta", not
"cluster-pool-v2".

Signed-off-by: Tobias Klauser <059b8b880f8441509ec8a65b50b4c6ae74ebea76@cilium.io>

cilium/cilium,cilium/cilium,cilium/cilium,cilium/cilium,cilium/cilium