[Rspamd] Add open-relay-check@mailcow.email to monitoring_nolog.map (#3757)

data/conf/rspamd/custom/monitoring_nolog.map

@@ -4,3 +4,4 @@
 /watchdog@localhost/i
 /supertool@mxtoolbox\.com/i
 /test@mxtoolboxsmtpdiag\.com/i
+/open-relay-check@mailcow\.email/i