Slight english readability fix for the signals docs.

.. data:: django.db.models.signals.post_syncdb

   :module:

Sent by :djadmin:`syncdb` command after it installs an application, and

Sent by the :djadmin:`syncdb` command after it installs an application, and the

:djadmin:`flush` command.

Any handlers that listen to this signal need to be written in a particular