fixtures: bump puppetlabs-puppet_agent to v4.19.0

Author: kenyon

.fixtures.yml

@@ -5,7 +5,7 @@ fixtures:
     facts: 'https://github.com/puppetlabs/puppetlabs-facts.git'
     puppet_agent:
       repo: 'https://github.com/puppetlabs/puppetlabs-puppet_agent.git'
-      ref: v4.13.0
+      ref: v4.19.0
     provision: 'https://github.com/puppetlabs/provision.git'
   symlinks:
     "apt": "#{source_dir}"