Fix Vagrant provisioning via the shells scripts don't work because of legacy apt repository

[movd]

Thanks for providing the sample environments!

The vagrant provisioning via the shells scripts didn't work anymore because the legacy repository was used.

The same patch versions as before aren't available on the new official project-owned repositories. Because of this, I upgraded to the next available patch level above the ones used before. There is a dedicated package repository for each Kubernetes minor version. That's why I extracted the first four characters as a quick fix.

After switching to the new apt repository, I ran into kubernetes/release#3276. I copied the sed fix from kubernetes/release#3279

I hope you have a great start to the new year! Thanks for your books!!

[movd]

My tests:

✅ Creates the 1.26 repository URLs used in most of the sample exercises:

$ vagrant ssh kube-control-plane
...
vagrant@kube-control-plane:~$ kubectl get nodes
NAME                 STATUS   ROLES           AGE     VERSION
kube-control-plane   Ready    control-plane   3m54s   v1.26.1
kube-worker-1        Ready    <none>          37s     v1.26.1
vagrant@kube-control-plane:~$ cat /etc/apt/sources.list.d/kubernetes.list 
deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.26/deb/ /

✅ Creates the 1.25 repository URLs needed for chapter 3 sample exercise 7:

$ vagrant ssh kube-control-plane
...
vagrant@kube-control-plane:~$ k get nodes
NAME                 STATUS   ROLES           AGE     VERSION
kube-control-plane   Ready    control-plane   3m31s   v1.25.6
kube-worker-1        Ready    <none>          50s     v1.25.6
vagrant@kube-control-plane:~$ cat /etc/apt/sources.list.d/kubernetes.list 
deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.25/deb/ /

$ vagrant ssh kube-worker-1
...
vagrant@kube-worker-1:~$ cat /etc/apt/sources.list.d/kubernetes.list
deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.25/deb/ /

✅ Fetching Logs for pods works

[bmuschko]

Thanks a lot for this fix! Merged. Happy New Year.