Mention Workaround for Vagrant 2.4.1 and VirtualBox 7.1

[Menkalian]

The latest versions of Vagrant (2.4.1) and VirtualBox (7.1) are incompatible to each other.
This is an open issue for vagrant: hashicorp/vagrant#13501

There exist workarounds to make them compatible (my personal preference is updating the VirtualBox provider to treat VBx 7.1 as VBx 7.0).

This workaround (or at least the known issue) should be mentioned in the slides and/or the relevant exercise. Otherwise many people might run into this issue when installing the latest versions of these tools.

[Menkalian]

I will provide a PR with suggestions for these changes.