Revert 231873 "Add a pointer to the supervised user dashboard to..."

> Add a pointer to the supervised user dashboard to the Settings page
> 
> It's hard for managers to know where to manage their users. Add a link to the
> dashboard under the Users section on the Settngs page, for users who are
> managing one or more supervised users.
> 
> BUG=298836
> 
> Review URL: https://codereview.chromium.org/27715002

TBR=pam@chromium.org

Review URL: https://codereview.chromium.org/53253002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231900 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231900