More stub methods to avoid flushing

v1_20_R2/src/main/java/net/citizensnpcs/nms/v1_20_R2/network/EmptyConnection.java

@@ -20,6 +20,10 @@ public class EmptyConnection extends Connection {
         };
     }
 
+    @Override
+    public void flushChannel() {
+    }
+
     @Override
     public boolean isConnected() {
         return true;

v1_20_R2/src/main/java/net/citizensnpcs/nms/v1_20_R2/network/EmptyPacketListener.java

@@ -13,6 +13,10 @@ public class EmptyPacketListener extends ServerGamePacketListenerImpl {
         super(minecraftServer, networkManager, entityPlayer, clc);
     }
 
+    @Override
+    public void resumeFlushing() {
+    }
+
     @Override
     public void send(Packet<?> packet) {
     }