Refs #15372 -- Removed obsolete docs about manage.py setting sys.path.

[chosak]

The current django-admin documentation page contains an outdated and incorrect description of what manage.py does.

The docs say that manage.py adds the project package to sys.path, but this is not true as of Django 1.4.

In versions of Django before 1.4, the manage.py script invoked logic that would add your project to sys.path. This code lived in django.core.management.setup_environ.

The changes to manage.py and the deprecation of this sys.path behavior were documented in the 1.4 release notes. It looks like the logic was removed in 1.6.