Revert "up vagrantfile"

This reverts commit 1f5aafbd.

Vagrantfile

@@ -19,7 +19,7 @@ Vagrant.configure("2") do |config|
      vb.customize ["modifyvm", :id, "--vram", 128]
      vb.customize ["modifyvm", :id, "--graphicscontroller","vboxsvga"]
      vb.customize ["modifyvm", :id, "--clipboard", "bidirectional"]
-     vb.customize ["modifyvm", :id, "--nested-hw-virt", "on"]
+     vb.customize ["modifyvm", :id, "--nested-hw-virt", on]
      vb.customize ["setextradata", "global", "GUI/SuppressMessages", "all" ]
   end