EZP-23805: Cleaned up vendor prefixes

JIRA: https://jira.ez.no/browse/EZP-23805

# Description

This patch cleans up the vendor prefixes in the CSS of PlatformUI. This is done according to [caniuse.com](http://caniuse.com/):

* http://caniuse.com/#feat=css-animation
* http://caniuse.com/#feat=css-transitions
* http://caniuse.com/#feat=transforms2d
* http://caniuse.com/#feat=transforms3d
* http://caniuse.com/#feat=css-boxshadow
* http://caniuse.com/#feat=css-gradients
* http://caniuse.com/#feat=css3-boxsizing

# Tests

manual tests
nope indeed, that was a leftover