Hi Cilium developers,

During trying to build a local vagrant environment, I realized that we can't use RUNTIME=docker option any longer and the default value became containerd since #19545.
However, the document is not updated.

In addition, according to helpers.bash, we can also use crio with the word cri-o, so we can modify the text like this:

• RUNTIME=x: Sets up the container runtime to be used inside a kubernetes cluster. Valid options are: containerd and crio (cri-o). If not set, it defaults to containerd.