Button to unbookmark a sound

[ffont]

If a sound has been bookmarked and we click on the "bookmark" button for that sound, it will be indicated in the bookmark modal that the sound has already been bookmarked. However there's no button to "unbookmark" the sound. The only way to do it is to navigate to the bookmark category page where it has been bookmarked to unbookmark it. We could add a button directly in the bookmark modal to unbookmark the sound.