CODECO operator deployment - requirements, br_filter and flannel - add to readme, deployment dependencies

During deployment, a requirement (due to flannel) is that the kernel module br_filter is active. By some reason, at least in Ubuntu 24.04 this does not happen by default.

It is important to add to the CODECO deployment readme a note that the Ubuntu kernel MUST have br_filter active.

As sudo, the following commands will activate br_filter:

tee /etc/modules-load.d/containerd.conf <<EOF br_netfilter EOF

modprobe br_netfilter