py-django3: updated to 3.1.3

Django 3.1.3 fixes several bugs in 3.1.2 and adds compatibility with Python 3.9.

Bugfixes

Fixed a regression in Django 3.1.2 that caused the incorrect height of the admin changelist search bar
Fixed a regression in Django 3.1.2 that caused the incorrect width of the admin changelist search bar on a filtered page
Fixed displaying Unicode characters in forms.JSONField and read-only models.JSONField values in the admin
Fixed a regression in Django 3.1 that caused a crash of ArrayAgg and StringAgg with ordering on key transforms for JSONField
Fixed a regression in Django 3.1 that caused a crash of __in lookup when using key transforms for JSONField in the lookup value
Fixed a regression in Django 3.1 that caused a crash of ExpressionWrapper with key transforms for JSONField
Fixed a regression in Django 3.1 that caused a migrations crash on PostgreSQL when adding an ExclusionConstraint with key transforms for JSONField in expressions
Fixed a regression in Django 3.1 where ProtectedError.protected_objects and RestrictedError.restricted_objects attributes returned iterators instead of set of objects
Fixed a regression in Django 3.1.2 that caused incorrect form input layout on small screens in the admin change form view
Fixed a regression in Django 3.1 that invalidated pre-Django 3.1 password reset tokens
Added support for asgiref 3.3
Fixed a regression in Django 3.1 that caused incorrect textarea layout on medium-sized screens in the admin change form view with the sidebar open
Fixed a regression in Django 3.0.7 that didn窶冲 use Subquery() aliases in the GROUP BY clause

(adam)