org-contribute.org: be more accurate about maximum length of tiny changes.
See http://bzr.savannah.gnu.org/lh/emacs/trunk/annotate/head:/etc/CONTRIBUTE:
"We can accept small changes (roughly, fewer than 15 lines) without legal
papers. Anything more substantial requires a copyright disclaimer or
assignment (the latter is preferred, especially for larger changes).
Both of these involved filling out a short form and filing it with the
FSF. The process is straightforward -- contact us at emacs-devel@gnu.org
to obtain the relevant forms."