Remove unused maxquerycount

While implementing the global limit 'max-query-count', initially I
thought adding the variable to the resolver structure. But the limit
is per client request so it was moved to the view structure (and
counter in ns_query structure). However, I forgot to remove the
variable from the resolver structure again. This commit fixes that.

(cherry picked from commit 397ca34e34)

lib/dns/resolver.c

@@ -582,7 +582,6 @@ struct dns_resolver {
 	unsigned int query_timeout;
 	unsigned int maxdepth;
 	unsigned int maxqueries;
-	unsigned int maxquerycount;
 	isc_result_t quotaresp[2];
 
 	/* Additions for serve-stale feature. */