Doc: typo

git-svn-id: svn://svn.savannah.gnu.org/texmacs/trunk@8795 64cb5145-927a-446d-8aed-2fb7b4773692
Minor addition


git-svn-id: svn://svn.savannah.gnu.org/texmacs/trunk@8796 64cb5145-927a-446d-8aed-2fb7b4773692