[Rspamd] Increase spam symbol weight

data/conf/rspamd/local.d/statistics_group.conf

@@ -1,6 +1,6 @@
 symbols = {
     "BAYES_SPAM" {
-        weight = 2.5;
+        weight = 4.5;
         description = "Message probably spam, probability: ";
     }
     "BAYES_HAM" {