nginx(role): simplify installation by removing version spec

We always just want the latest anyway and therefore don't use it, so no
need to keep the complexity introduced by that setting.
Also merge repo_setup and nginx_install task lists into one
nginx_install task list as keeping two files isn't necessary.
Finally improving naming a bit.

roles/nginx/tasks/main/nginx_install.yaml

@@ -44,7 +44,7 @@
     mode: "0644"
   become: true
 
-- name: Ensure NGINX is installed
+- name: Ensure nginx is installed
   ansible.builtin.apt:
     name: nginx
     state: present