Bug 865407 - Part 9: Remove border-box and padding CSS on the caption overlay. r=rillian

This wasn't working correctly. Vtt.js now takes care of applying padding
to the video overlay.

layout/style/html.css

@@ -729,8 +729,6 @@ audio:not([controls]) {
 video > .caption-box {
   position: relative;
   overflow: hidden;
-  padding: 1.5%;
-  box-sizing: border-box;
 }
 
 /* emulation of non-standard HTML <marquee> tag */