Update button labeling #659

Right now, Able Player's buttons use an aria-label, internal screen reader text, and have a visible tooltip generated from the aria-label.

This goes back to #81, because JAWS wasn't able to read buttons without innerText. (E.g., didn't support aria-label. This is no longer true, and this should be simplified.

The simplest change is to eliminate the able-clipped container inside buttons. It might be better to offer support for auto translation by retaining screen reader text; I'm just not sure it's worth it. The package is already translated into dozens of languages, so this would be an edge scenario.

Right now, however, the able-clipped container does not serve any purpose; it's overridden by the aria-label.