typo fix

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@2610 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

TODO

@@ -6,7 +6,7 @@ For version 1.4:
 - Support for paragraph searches. [DONE]
 - Support for justifying the entire file at once. [DONE]
 - Support for filename searches in the file browser.
-- Undo/Redo key?
+- Undo/Redo keys?
 - Rebindable keys?
 - Keystroke to implement "Add next sequence as raw" like vi's ^V. [DONE]
 - Spell check selected text only. [DONE]