Update spec URLs for VisualViewport events (#15701)
Update spec URLs for VisualViewport events (#15701)

A recent spec change removed the anchor we were using. The spec doesn’t
give us ideal anchors for these events, but these updates point readers
to somewhere reasonably useful.
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data