pkgng: remove redundant test for docker container

These tests should be skip/docker, but the test
playbook also redundantly checked whether it was
running in a docker container.

Checking whether `ansible_facts.distribution` is
`FreeBSD` is really sufficient to be sure whether
the test is running in an environment that supports
the `pkgng` module.

tests/integration/targets/pkgng/tasks/main.yml

@@ -1,7 +1,6 @@
 ---
 - name: Test on FreeBSD VMs
   when:
-    - ansible_facts.virtualization_type != 'docker'
     - ansible_facts.distribution == 'FreeBSD'
   block:
     ##