Get rid of initializeTouchEvents

We don't need it any more, thanks to @yungsters's 4deb0d61. Before that we weren't getting click events regardless of whether touch events were initialized, which was (as far as I know) the only thing to be worried about with this change.

We could also keep initializeTouchEvents around for API compatibility and make it a noop, but I don't think anyone here really cares about keeping it.

Test Plan:
On an iPad, verified that a single element can receive touchstart, touchmove, touchend, mousedown, mouseup, and click events all at the same time (with a single tap, no less!).