minor clean: uniform cast style

Author: slandelle

client/src/main/java/org/asynchttpclient/netty/handler/AsyncHttpClientHandler.java

@@ -133,7 +133,7 @@ public void channelInactive(ChannelHandlerContext ctx) throws Exception {
             callback.call();
 
         } else if (attribute instanceof NettyResponseFuture<?>) {
-            NettyResponseFuture<?> future = NettyResponseFuture.class.cast(attribute);
+            NettyResponseFuture<?> future = (NettyResponseFuture<?>) attribute;
             future.touch();
 
             if (hasIOExceptionFilters && requestSender.applyIoExceptionFiltersAndReplayRequest(future, ChannelClosedException.INSTANCE, channel))