jmri: remove one-shot xpra migration task (idempotency fix)

Migration from Ubuntu 3.x to upstream 6.x is complete. The explicit
removal task was firing changed on every run. state: latest on the
install task handles upgrades going forward.

ansible/roles/jmri/tasks/main.yml

@@ -323,12 +323,6 @@
     path: "{{ jmri_home }}/.vnc"
     state: absent
 
-- name: Remove Ubuntu-packaged xpra (too old — v3.x, incompatible with v6 client)
-  ansible.builtin.apt:
-    name: xpra
-    state: absent
-  when: "'xpra' in ansible_facts.packages and ansible_facts.packages['xpra'][0].source != 'xpra.org'"
-
 - name: Install xpra.org apt signing key
   ansible.builtin.get_url:
     url: https://xpra.org/gpg.asc