cloud0: Exclude Nextcloud trash from backups

Files in the Nextcloud trash bin do not need to be backed up.  They are
often large (i.e. my Signal backups), and presumably, they are not
needed anyway; why would they be in the trash otherwise?

host_vars/cloud0.pyrocufflink.blue.yml

@@ -1,3 +1,4 @@
 burp_backup:
 - include: /var/lib/nextcloud/apps
 - include: /var/lib/nextcloud/data
+- exclude_regex: /var/lib/nextcloud/data/[^/]+/files_trashbin