fix(tasks): stop reporting a change when looking up the btrfs device

`findmnt` only reads the mount table, but the task declared `changed_when` on a successful return code and therefore
reported a change on every single run. Any btrfs backed user made the whole play non idempotent, which an idempotence
check would flag as soon as one exists.

The `failed_when` on a non zero return code is dropped along with it, since that is exactly what the command module does
by default.

Co-authored-by: Copilot <copilot@github.com>

tasks/create_unix_user.yaml

@@ -12,8 +12,7 @@
     ansible.builtin.command:
       cmd: /bin/bash -c "findmnt -no SOURCE -T {{ user_user_home }} | sed 's/\[.*\]//'"
     register: _unix_users_btrfs_device
-    failed_when: _unix_users_btrfs_device.rc != 0
-    changed_when: _unix_users_btrfs_device.rc == 0
+    changed_when: false
 
   - name: "Determine filesystem of device"
     ansible.builtin.set_fact: