Fix display on mobile.

[Dorus]

See https://github.com/gcp/leela-zero/issues/412#issuecomment-353960893

If black passes, you need to scroll at the bottom to see the result.

Before scroll:

After scroll:

There are 2 problems with the CSS:

wgo.player.css:375

.wgo-player-top .wgo-comments-content, .wgo-player-bottom .wgo-comments-content {
    position: absolute;
}

Here "absolute" should be "relative".

wgo.player.css:394

.wgo-player-top .wgo-comments-wrapper, .wgo-player-bottom .wgo-comments-wrapper {
    height: 150px;
}

Here should be no height indication.