FAI using NFS v4 with the nfsroot

Hi,
if there's no severe downside of using NFSv4 I would like to use it with
nfsroot.
In the docu I found this:
"[...] If you want to use NFS v4 for the nfsroot, you have to remove
this option the the kernel boot options."

On my FAI server I can list the configuration for all hosts:
root@faiserver:~# fai-chboot
-L                                                                                                                                         

[DEFAULT] default localboot -1
[Other] nas vmlinuz-5.8.0-0.bpo.2-amd64 initrd=initrd.pxe ip=dhcp 
root=/dev/nfs nfsroot=faiserver:/srv/fai/nfsroot-nas rootovl
ipv6.disable=1 ip=:::::eno1             
nas C0A801C9 vmlinuz-5.8.0-0.bpo.2-amd64
initrd=initrd.img-5.8.0-0.bpo.2-amd64 ip=dhcp 
root=/srv/fai/nfsroot-diskless:vers=3 rootovl 
FAI_FLAGS=verbose,sshd,createvt
FAI_CONFIG_SRC=nfs://faiserver/srv/fai/config FAI_ACTION=install

Can you please advise how to remove the kernel boot option with fai-chboot?

THX