All: remove unused .chromeframe rule

Was used around 2014 as part of the HTML5 Boilerplate at the time,
but that was a long time ago.

Author: Krinkle

themes/jquery/css/base.css

@@ -98,13 +98,6 @@ body {
 	background: #c9f2c8;
 }
 
-.chromeframe {
-	margin: 0.2em 0;
-	background: #ccc;
-	color: #000;
-	padding: 0.2em 0;
-}
-
 /* ==========================================================================
    FontAwesome (https://fontawesome.com/v3/)
 	 .ttf and .woff files were included in the FontAwesome download.