fix typo in tutorial

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/tutorial.txt

@@ -103,7 +103,7 @@ newly modified content to the index.  Finally, commit your changes with:
 $ git commit
 ------------------------------------------------
 
-This will again prompt your for a message describing the change, and then
+This will again prompt you for a message describing the change, and then
 record a new version of the project.
 
 Alternatively, instead of running `git add` beforehand, you can use