fix sytnax error

roles/fai/tasks/apt-cacher-ng.yml

@@ -38,14 +38,14 @@
     mode: u=rw,g=r,o=r
   register: apt_cacher_config
 
-- name:
-    copy:
-      content: |
-        http://archive.ubuntu.com/ubuntu/
-      dest: /etc/apt-cacher-ng/backends_ubuntu
-      owner: root
-      group: root
-      mode: u=rw,g=r,o=r
+- name: set ubuntu server as backend
+  copy:
+    content: |
+      http://archive.ubuntu.com/ubuntu/
+    dest: /etc/apt-cacher-ng/backends_ubuntu
+    owner: root
+    group: root
+    mode: u=rw,g=r,o=r
 
 - name: ensure service is started and enabled
   service: