netty: Backport SETTINGS ACK sequencing fix

This fix was made in netty/netty#6521. Fixes #2801

netty/third_party/netty/java/io/grpc/netty/FixedHttp2ConnectionDecoder.java

@@ -450,11 +450,11 @@ public class FixedHttp2ConnectionDecoder implements Http2ConnectionDecoder {
 
         @Override
         public void onSettingsRead(ChannelHandlerContext ctx, Http2Settings settings) throws Http2Exception {
-            encoder.remoteSettings(settings);
-
             // Acknowledge receipt of the settings.
             encoder.writeSettingsAck(ctx, ctx.newPromise());
 
+            encoder.remoteSettings(settings);
+
             listener.onSettingsRead(ctx, settings);
         }