[Rspamd] Remove unused user_keywords and dynamic_rates from ratelimit module

data/conf/rspamd/override.d/ratelimit.conf

@@ -9,5 +9,3 @@ rates {
 whitelisted_rcpts = "postmaster,mailer-daemon";
 max_rcpt = 5;
 custom_keywords = "/etc/rspamd/lua/ratelimit.lua";
-user_keywords = ["customrl"];
-dynamic_rates = { customrl = "customrl"}