Correct migrations according to PR suggestions

.isort.cfg

calendar_utils/models.py

...rations/0107_districtcenterpage_calendar_page_and_more.py

district/migrations/0109_districtcalendarpage_and_more.py

district/models.py

...gn/migrations/0011_senatcampaignhomepage_calendar_page.py

uniweb/migrations/0040_uniwebhomepage_calendar_page.py

...s/0042_uniwebcalendarpage_uniwebhomepage_calendar_page.py

uniweb/models.py