Do not run specs on Ubuntu 16.04

.kitchen.dokken.yml

@@ -15,10 +15,6 @@ verifier:
   name: inspec
 
 platforms:
-  - name: ubuntu-16.04
-    driver:
-      image: dokken/ubuntu-16.04
-      pid_one_command: /bin/systemd
   - name: ubuntu-18.04
     driver:
       image: dokken/ubuntu-18.04

.kitchen.yml

@@ -6,7 +6,6 @@ provisioner:
   name: chef_zero
 
 platforms:
-  - name: ubuntu-16.04
   - name: ubuntu-18.04
   - name: debian-9