Fix focus state for links containing inline code

Inheriting the background from the link means that the code block ends up with its own yellow background, which then clips the box-shadow used to give the focused link a black underline.

Rather than inherit the yellow background, set the background to transparent. The focused link still has its own yellow background which can be seen ‘through’ the transparent code element.

lib/assets/stylesheets/modules/_technical-documentation.scss

@@ -185,7 +185,7 @@
   }
 
   a:focus code {
-    background: inherit;
+    background: transparent;
     color: inherit;
   }