Sync specs.less with {print,screen}.css (#1710)

In ceb6655663 (#2130), CSS code has been
changed in src/main/html/csss/{print,screen}.css instead of LESS source.
This commit resynchronize the source with the generated code.

src/main/less/specs.less

@@ -530,6 +530,7 @@
             margin: 0 0 10px 0;
             code {
                 line-height: 1.6em;
+                overflow: auto;
             }
         }
     }