rustdoc: merge common CSS for a

Author: notriddle

src/librustdoc/html/static/css/rustdoc.css

@@ -253,6 +253,7 @@ h1 a,
 
 a {
 	color: var(--link-color);
+	text-decoration: none;
 }
 
 ol, ul {
@@ -662,10 +663,6 @@ nav.sub {
 	margin: 0 0 15px 0;
 }
 
-a {
-	text-decoration: none;
-}
-
 .small-section-header {
 	/* fields use <span> tags, but should get their own lines */
 	display: block;