Rspamd Plugin - wrong error message

The error message here https://git.ispconfig.org/ispconfig/ispconfig3/blob/3.1.15/server/plugins-available/rspamd_plugin.inc.php#L148 is wrong and was copied from the line above, please update it.

(I found it accidentally as I am investigating an error message on my updated system where I started using rspamd. Thanks for this very much appreciated new support of rspamd)