Fix typo in readme.
Fix typo in readme.

infernix/vagrant-libvirt,infernix/vagrant-libvirt,pradels/vagrant-libvirt,vagrant-libvirt/vagrant-libvirt,vagrant-libvirt/vagrant-libvirt,electrofelix/vagrant-libvirt,pradels/vagrant-libvirt,skamithi/vagrant-libvirt,vagrant-libvirt/vagrant-libvirt,electrofelix/vagrant-libvirt,sendgrid-ops/vagrant-libvirt,skamithi/vagrant-libvirt,sendgrid-ops/vagrant-libvirt,infernix/vagrant-libvirt,electrofelix/vagrant-libvirt