rustdoc: remove unused CSS .sub-settings

Obsoleted when 9625ed8 changed the DOM.

Author: notriddle

src/librustdoc/html/static/css/settings.css

@@ -59,12 +59,6 @@
 	cursor: pointer;
 }
 
-.setting-line > .sub-settings {
-	padding-left: 42px;
-	width: 100%;
-	display: block;
-}
-
 #settings .setting-line {
 	margin: 1.2em 0.6em;
 }