LPS-48502 - Remove 'unescapeHTML' method from Liferay.Util

Hi Nate,

Attached is an update for https://issues.liferay.com/browse/LPS-48502.

There are instances of ```Liferay.Util.unescapeHTML``` being used in plugins as well, so I will send you another pull for those.

Please let me know if there are any issues.

Thanks!