Remove urgent requests from prefetch queue

This stops us from responding twice if a prefetch request is upgraded to
urgent by the client.

Signed-off-by: Graham <gpe@openrs2.org>

game/src/main/kotlin/org/openrs2/game/net/js5/Js5Client.kt

@@ -13,6 +13,7 @@ public class Js5Client(
         if (request.prefetch) {
             prefetch += request
         } else {
+            prefetch -= request
             urgent += request
         }
     }