Rename all j2 files to templates

Not according to convention, but it reads better.

roles/owner/tasks/main.yml

@@ -39,7 +39,7 @@
 
 - name: 'Set up environment variables for user "{{ owner_name }}".'
   ansible.builtin.template:
-    src: env.j2
+    src: env.template
     dest: "/home/{{ owner_name }}/.env"
     owner: "{{ owner_name }}"
     group: "{{ owner_group }}"