fix: fix `ifinstalled` tag for Django 3+
fix: fix `ifinstalled` tag for Django 3+

Fixes #1972

jerivas/mezzanine,stephenmcd/mezzanine,dsanders11/mezzanine,jerivas/mezzanine,stephenmcd/mezzanine,stephenmcd/mezzanine,dsanders11/mezzanine,jerivas/mezzanine,dsanders11/mezzanine