change highlight color from green to yellow

(fits better in the color scheme).

eliminate background color on line numbers at
bottom of search results, now that they are grouped.

live at http://r45:3456/search?q=Reader

R=r, gri
http://go/go-review/1024030

doc/style.css

@@ -185,7 +185,6 @@ a.noline {
 
 a.info {
   text-decoration: none;
-  background-color: #D8D8D8;
 }
 
 table.layout {
@@ -199,7 +198,7 @@ span.comment {
 }
 
 span.highlight {
-  background-color: #81F781;
+  background-color: #ffffa0;
 }