API docs: Removed stray div.

This fixes the issue with the left sidebar incorectly flowing to
the bottom of the page.

Signed-off-by: Mavridis Philippe <mavridisf@gmail.com>

doc/common/footer.html

@@ -1,6 +1,5 @@
           </div>
         </div>
-        </div>
         <div id="left">
           <div class="menu_box">
 <a name="cp-menu" /><div class="menutitle"><div>

doc/common/mainfooter.html

@@ -13,7 +13,6 @@ Questions about the reference manuals should be sent to
 </div>
           </div>
         </div>
-        </div>
         <div id="left">
           <div class="menu_box">