Swap to use Ubuntu for demo as well

It doesn't actually matter what box we use - might as well be the same
one as for Vagrant runner.

README.md

@@ -93,11 +93,6 @@ Run `DHCP_RANGE_START=192.168.0.1 vagrant up netboot demo`.
 
 You'll probably be prompted twice for the network to attach to.
 
-### Running the demo on Windows with Virtualbox
-Unfortunately the PXE boot box used for the demo is only built for Virtualbox,
-if you're using Hyper-V you'll have to create yourself a VM and configure it
-to boot from the network (disable Secure Boot too, probably).
-
 ## Building Locally
 Should be as simple as `docker build .`
 

Vagrantfile

@@ -4,7 +4,7 @@
 Vagrant.configure("2") do |config|
   # Define a Vagrant machine which should PXE boot off the docker cotnainer
   config.vm.define :demo, primary: true do |demo|
-    demo.vm.box = "clink15/pxe"
+    demo.vm.box = "bento/ubuntu-20.04"
 
     # Bridge the VM onto your host's network
     demo.vm.network "public_network"