Hide vagrant 2.0+ messages about ansible auto compatibility_mode

Vagrant has automatically selected the compatibility mode '2.0'
according to the Ansible version installed (2.4.0.0).

Alternatively, the compatibility mode can be specified in your Vagrantfile:
https://www.vagrantup.com/docs/provisioning/ansible_common.html#compatibility_mode

Vagrantfile

@@ -108,6 +108,7 @@ Vagrant.configure('2') do |config|
  config_dir: config_dir,
  drupalvm_env: drupalvm_env
  }
+ ansible.compatibility_mode = '2.0'
  ansible.raw_arguments = ENV['DRUPALVM_ANSIBLE_ARGS']
  ansible.tags = ENV['DRUPALVM_ANSIBLE_TAGS']
  ansible.verbose = ENV['DRUPALVM_DEBUG']