Visibility not updated on revealed elements in IE 11

The example used on the [User Experience](https://scrollrevealjs.org/guide/user-experience.html) page to "Prevent Flickering" suggests adding a "visibility: hidden" style to items that will transition, but this isn't working in IE 11. ScrollReveal doesn't seem to update the visibility on revealed elements in IE 11.

The problem can be seen in your example demo: https://jsbin.com/fuvusofere/edit?html,css,output

I ran this thru WebPageTest to confirm it wasn't just my local setup that had the issue.

https://www.webpagetest.org/result/210413_AiDc2R_dc0e38e7c29f55599d9512320d9ec0c5/


### Environment

* Operating System: Windows 10
* Browser Version: IE 11
* ScrollReveal Version: 4.0.9

Start with the “Prevent Flickering” example on the User Experience page and reproduce the behavior in IE 11 using the linked JS Bin demo. Trace how ScrollReveal 4.0.9 handles visibility when elements are revealed; done means the visibility style is updated correctly in IE 11, matching behavior in other browsers.

Written by the indexing model from the issue text.