legacy-chat: fix cancel on < 1.19

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/legacy/LegacyChatHandler.java

@@ -45,7 +45,7 @@ public class LegacyChatHandler implements ChatHandler<LegacyChat> {
     }
     this.server.getEventManager().fire(new PlayerChatEvent(this.player, packet.getMessage()))
         .whenComplete((chatEvent, throwable) -> {
-          if (chatEvent.getResult().isAllowed()) {
+          if (!chatEvent.getResult().isAllowed()) {
             return;
           }