[Rspamd] Slightly reduce map watch interval

data/conf/rspamd/local.d/options.inc

@@ -1,7 +1,7 @@
 dns {
   enable_dnssec = true;
 }
-map_watch_interval = 60s;
+map_watch_interval = 30s;
 dns {
   timeout = 4s;
   retransmits = 5;