Replace some CentOS references to support other RHEL derivatives

Not hardcoding 'CentOS' and using the OS family ('RedHat') instead,
we now behave better on Rockylinux and AlmaLinux, etc.

With that said, we may or may not fully support CentOS/Rockylinux/AlmaLinux v8 yet.
Certain things were improved in
https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300.

v8 support is discussed here: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300
Certain things (firewalld?) may still be problematic. This patch does not try to address those.
If the remaining issues are confirmed to be fixed in the future, we can mark v8 as supported.

roles/matrix-ma1sd/tasks/setup_install.yml

@@ -62,10 +62,10 @@
       update_cache: yes
     when: (ansible_os_family == 'Debian')
 
-  - name: Ensure gradle is installed for self-building (CentOS)
+  - name: Ensure gradle is installed for self-building (RedHat)
     fail:
-      msg: "Installing gradle on CentOS is currently not supported, so self-building ma1sd cannot happen at this time"
-    when: ansible_distribution == 'CentOS'
+      msg: "Installing gradle on RedHat ({{ ansible_distribution }}) is currently not supported, so self-building ma1sd cannot happen at this time"
+    when: ansible_os_family == 'RedHat'
 
   - name: Ensure gradle is installed for self-building (Archlinux)
     pacman: