Pass all package names to "apt" module instead of using a loop
This fixes a warning:
"[DEPRECATION WARNING]: Invoking "apt" only once while using a loop
via squash_actions is deprecated. Instead of using a loop to
supply multiple items and specifying `name: "{{item}}"`, please
use `name: '{{backup_apt_dependencies}}'` and remove the loop.
This feature will be removed in version 2.11. Deprecation warnings
can be disabled by setting deprecation_warnings=False in ansible.cfg."