Docserver: Remove .html from the links in the sidenav.

R=mkearney@chromium.org

Review URL: https://codereview.chromium.org/164813002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251195 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251195