nginx(role): simplify ensuring that gnupg is installed

Also improve naming.

roles/nginx/tasks/main/nginx_install.yaml

@@ -1,14 +1,8 @@
-- name: gather package facts
+- name: Ensure gnupg is installed
-  ansible.builtin.package_facts:
-    manager: apt
-
-- name: make sure `gnupg` package is installed
   ansible.builtin.apt:
     name: gnupg
     state: present
-    update_cache: true
   become: true
-  when: "'gnupg' not in ansible_facts.packages"
 
 - name: make sure NGINX signing key is added
   ansible.builtin.get_url: