[Rspamd] Olefy: reduce max scan size to 5 MiB

data/conf/rspamd/local.d/external_services.conf

@@ -6,4 +6,5 @@ oletools {
   # mime-part regex matching in content-type or filename
   # block all macros
   extended = true;
+  max_size = 5242880;
 }