Remove redundant overflowing rule

Author: artemshitov

src/rustbook/static/rustbook.css

@@ -44,7 +44,6 @@ h1, h2, h3, h4, h5, h6 {
 
     #page-wrapper {
         position: absolute;
-        overflow-y: auto;
         left: 310px;
         right: 0px;
         top: 0px;