Remove KOLIBRI_USER (kolibri) secondary group 'disk'

roles/kolibri/tasks/install.yml

@@ -26,9 +26,8 @@
 - name: Create Linux user {{ kolibri_user }} and add it to groups {{ apache_user }}, disk
   user:
     name: "{{ kolibri_user }}"
-    groups:
-      - "{{ apache_user }}"
-      - disk    # 2023-03-27: IS THIS REALLY NECESSARY? Unclear. "Mostly equivalent to root access" according to https://wiki.debian.org/SystemGroups
+    groups: "{{ apache_user }}"    # 2023-03-29: Not really necessary (Kolibri is demonstrated to work without group 'www-data').  But it likely doesn't hurt.
+      #- disk    # 2023-03-29: Tested to be unnec with USB sticks (with 64-bit RasPiOS).  FWIW group 'disk' is "Mostly equivalent to root access" according to https://wiki.debian.org/SystemGroups
     state: present
     shell: /bin/false
     system: yes