Now that we're on a modern version of Django, we no longer need to worry

about capping the version of the psycopg2-binary dependency for

Postgres. We previously needed to cap it in order to avoid a

compatibility issue with newer versions of the package and older

versions of Django.
This change removes the cap. At this point, any version installed is

considered fine for our needs.

Installed the package via ReviewBoard[postgres] successfully.