common: backup_autoremove: force rm

so no error occurs because no parameter was given

roles/common/templates/backup_autoremove.sh

@@ -17,5 +17,5 @@ find {{ backups_directory | quote }} -type f |
   getDirName |
   sort --unique |
   while read dir; do
-  find "$dir" -type f | onlyDatedFiles | sort --reverse | tail --lines=+$((backupsToKeep + 1)) | xargs rm;
+  find "$dir" -type f | onlyDatedFiles | sort --reverse | tail --lines=+$((backupsToKeep + 1)) | xargs rm --force;
 done