Remove Vagrant agent for Debian 8 as it is no longer supported.

Debian 8 is EOL (end of life) and has already stopped being supported by
this module.

Vagrantfile

@@ -155,18 +155,6 @@ Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
     agent.vm.provision :shell, :inline => "facter --custom-dir=/vagrant/lib/facter sensu_agent"
   end
 
-  config.vm.define "debian8-agent", autostart: false do |agent|
-    agent.vm.box = "debian/jessie64"
-    # TODO: Use specific version as something broken with 8.11.1
-    # See https://github.com/sensu/sensu-puppet/pull/1234#issuecomment-605355385
-    agent.vm.box_version = '8.11.0'
-    agent.vm.hostname = 'debian8-agent.example.com'
-    agent.vm.network  :private_network, ip: "192.168.52.17"
-    agent.vm.provision :shell, :path => "tests/provision_basic_debian.sh"
-    agent.vm.provision :shell, :inline => "puppet apply /vagrant/tests/sensu-agent.pp"
-    agent.vm.provision :shell, :inline => "facter --custom-dir=/vagrant/lib/facter sensu_agent"
-  end
-
   config.vm.define "win2012r2-agent", autostart: false do |agent|
     agent.vm.box = "opentable/win-2012r2-standard-amd64-nocm"
     agent.vm.provider :virtualbox do |vb|