doc: status.showUntrackedFiles does not take "false"

The `status.showUntrackedFiles` config option only accepts the
values "no", "normal" or "all", but not as this part of the man page
suggested "false".  While we are at it, camel-case the name of the
variable.

Signed-off-by: Jonas Wunderlich <git@03j.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jonas-w

Documentation/git-status.txt

@@ -472,7 +472,7 @@ again, because your configuration may already be caching `git status`
 results, so it could be faster on subsequent runs.
 
 * The `--untracked-files=no` flag or the
-	`status.showUntrackedfiles=false` config (see above for both):
+	`status.showUntrackedFiles=no` config (see above for both):
 	indicate that `git status` should not report untracked
 	files. This is the fastest option. `git status` will not list
 	the untracked files, so you need to be careful to remember if