Captions: Fix test that's disabled on IE8, testing iOS7 functionality

[gkatsev]

We have a test that tests our shimming of the onchange for iOS7. It is currently disabled on IE8 because it's failing there for some reason.
We need to investigate why it's broken on IE8 and fix it.

[gkatsev]

So, looks like the test is broken because you can't trigger custom events on IE8 and document.createEvent doesn't exist there either.
The reason why we need document.createEvent is so that we can trigger a manual change event for iOS7. I can change the test to do feature detection for document.createEvent if that's better, otherwise, I think it's ok to leave as is.
@videojs/core-committers thoughts?

[gkatsev]

I'm going to close this because IE8 is the only browser we support that doesn't support createEvent, so, it's more or less synonymous.