[1.7.x] Fixed typo in docs/ref/django-admin.txt

In addition, ``manage.py`` is automatically created in each Django project.

``manage.py`` is a thin wrapper around ``django-admin.py`` that takes care of

two things for you before delegating to ``django-admin.py``:

several things for you before delegating to ``django-admin.py``:

* It puts your project's package on ``sys.path``.