ansible: use apt ansible task to autoremove

Ansible's builtin `apt` task has had an `autoremove` option since
version 2.1 of the builtin. Using the builtin task rather than
directly running `apt` will correctly set the `DEBIAN_FRONTEND`
environment variable to `noninteractive` to prevent user prompts
from packages which would otherwise cause `apt` to wait for user
input (which will never come when run via Ansible).

ansible/roles/package-upgrade/tasks/partials/apt.yml

@@ -16,6 +16,6 @@
   environment:
     FLASH_KERNEL_SKIP: true
 
-  # don't know how to use autoremove=yes for all packages
 - name: clean unwanted packages
-  command: apt-get -y autoremove warn=False
+  apt:
+    autoremove: yes