Upgrade to Wagtail 2.16.1 and Django 4

.../migrations/0043_alter_districtarticletag_tag_and_more.py

...2021/migrations/0050_alter_elections2021articletag_tag.py

majak/urls.py

...8_alter_regionarticletag_tag_alter_regionpersontag_tag.py

requirements/base.in

requirements/base.txt

requirements/dev.txt

requirements/production.txt

uniweb/migrations/0021_alter_uniwebarticletag_tag.py