[Fix] Update is_spam in learned_ids when relearning

lualib/redis_scripts/bayes_cache_learn.lua

   local have = redis.call('HGET', prefix, cache_id)
 
   if have then
-    -- Already in cache
+    -- Already in cache, but is_spam changes when relearning
+    redis.call('HSET', prefix, cache_id, is_spam)
     return false
   end
 end
   end
 end
 
-return true
+return true