spellcheck: do not use enchant

NorvigSpellCheck does everything we need it to do so remove the
enchant import-override.

Our spellchecker supports add_word(), which is used to add the
user's name and email address to the dictionary.  We would want
to do the same with Enchant is we were to go down that route.

Signed-off-by: David Aguilar <davvid@gmail.com>