Remove obsolete .reload-module-on-update file

It does not serve any function anymore after support for module
reloading has been removed from the postinst script in 0.0.20200215-2 on
2020-02-24. A module update is properly signaled via
/run/reboot-required so that the admin can (automatically) schedule a
reboot when convenient. This will also be more in line with future Debian
releases because starting with Debian bullseye, the kernel ships the
module.

tasks/main.yml

@@ -114,18 +114,10 @@
   notify:
     - reconfigure wireguard
 
-- name: Check if reload-module-on-update is set
-  stat:
-    path: "{{ wireguard_remote_directory }}/.reload-module-on-update"
-  register: reload_module_on_update
-  tags:
-    - wg-config
-
-- name: Set WireGuard reload-module-on-update
+- name: Ensure legacy reload-module-on-update is absent
   file:
     dest: "{{ wireguard_remote_directory }}/.reload-module-on-update"
-    state: touch
-  when: not reload_module_on_update.stat.exists
+    state: absent
   tags:
     - wg-config