About: Swap out images and videos for CDN versions, and add responsive images.

Props: joemcgill, pento.
See #40721. 


git-svn-id: https://develop.svn.wordpress.org/trunk@40881 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/about.css

@@ -40,7 +40,6 @@
 	max-width: 100%;
 	height: auto;
 	vertical-align: middle;
-	border: 1px solid rgba(0, 0, 0, 0.1);
 }
 
 .about-wrap .jetpack-video-wrapper {
@@ -294,10 +293,6 @@
 	padding-top: 35px;
 }
 
-.about-wrap .headline-feature img {
-	border: none;
-}
-
 .about-wrap .feature-section .media-container {
 	overflow: hidden;
 }