Removes unecessary lines.

Not sure what is the objective of these lines, bt I think they are useless.
Check the doc here to be sure:
https://docs.ansible.com/ansible/latest/plugins/lookup/inventory_hostnames.html

tasks/main.yml

@@ -67,8 +67,6 @@
 - name: Generate WireGuard private key
   shell: "wg genkey"
   register: wg_private_key_result
-  with_inventory_hostnames:
-    - vpn
   when: not private_key_file_stat.stat.exists
   tags:
     - wg-generate-keys
@@ -85,8 +83,6 @@
   shell: "echo '{{ wg_private_key }}' | wg pubkey"
   register: wg_public_key_result
   when: not private_key_file_stat.stat.exists
-  with_inventory_hostnames:
-    - vpn
   tags:
     - wg-generate-keys