Is the stone click sound painful or distracting to you?
Add the following rules to ublock origin:
cdn.online-go.com/5.0/sound/stone1.ogg
cdn.online-go.com/5.0/sound/stone2.ogg
cdn.online-go.com/5.0/sound/stone3.ogg
cdn.online-go.com/5.0/sound/stone4.ogg
cdn.online-go.com/5.0/sound/stone5.ogg
cdn.online-go.com/5.0/sound/stone1.mp3
cdn.online-go.com/5.0/sound/stone2.mp3
cdn.online-go.com/5.0/sound/stone3.mp3
cdn.online-go.com/5.0/sound/stone4.mp3
cdn.online-go.com/5.0/sound/stone5.mp3
cdn.online-go.com/5.0/sound/stone1.wav
cdn.online-go.com/5.0/sound/stone2.wav
cdn.online-go.com/5.0/sound/stone3.wav
cdn.online-go.com/5.0/sound/stone4.wav
cdn.online-go.com/5.0/sound/stone5.wav
Then you can still hear the countdown, but the stone sound is gone.