fix(ceph-grafana): make dashboard download work again

This fixes the dashboard download for pacific and later.

Signed-off-by: Michael Wagner <mitch.wagna@gmail.com>
(cherry picked from commit 4edaab5)

roles/ceph-grafana/tasks/configure_grafana.yml

@@ -36,7 +36,7 @@
 
 - name: download ceph grafana dashboards
   get_url:
-    url: "https://raw.githubusercontent.com/ceph/ceph/{{ grafana_dashboard_version }}/monitoring/grafana/dashboards/{{ item }}"
+    url: "https://raw.githubusercontent.com/ceph/ceph/{{ grafana_dashboard_version }}/monitoring/ceph-mixin/dashboards_out/{{ item }}"
     dest: "/etc/grafana/dashboards/ceph-dashboard/{{ item }}"
   with_items: "{{ grafana_dashboard_files }}"
   when: