[Minor] config: remove RBL defaults that re-enforce true defaults

conf/modules.d/rbl.conf

@@ -14,12 +14,7 @@
 
 rbl {
   default_exclude_users = true;
-  default_exclude_local = true;
   default_unknown = true;
-  default_dkim_domainonly = true;
-  default_dkim_match_from = false;
-  default_ipv4 = true;
-  default_ipv6 = true;
 
   url_whitelist = [
     "https://maps.rspamd.com/rspamd/surbl-whitelist.inc.zst",