Yes, as long as you submitted your game by the deadline and it's in the submission list, you can update it. However, we cannot guarantee that the judges will play the most updated build, as we can't tell exactly when your game will be judged.
Viewing post in Possible to update page for performance fixes?
Thanks! I just pushed an update that improves performance on browser and Android. Also got some bugs fixed, including a pretty game-breaking one on Android that resulted in the screen not loading properly. I also noticed that Godot 4 doesn't run great without hardware acceleration in the browser so I've put a note on my page about that too.