Fix docstring of project.Project.PrintWorkTreeStatus()

Change-Id: I1a9139d2ea3b3331a6f3ad3cae9e0ac37074d716
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/251837


Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Rostislav Krasny <rostigm@gmail.com>