r/wal-g-pg: Schedule weekly delete jobs

WAL-G slows down significantly when too many backups are kept.  We need
to periodically clean up old backups to maintain a reasonable level of
performance, and also keep from wasting space with useless old backups.

roles/wal-g-pg/handlers/main.yml

@@ -6,3 +6,8 @@
   systemd:
     name: wal-g-backup.timer
     state: restarted
+
+- name:  restart wal-g delete timer
+  systemd:
+    name: wal-g-delete.timer
+    state: restarted