Bump Django version to 2.2

[MauricioFauth]

• Depends on https://github.com/phpmyadmin/website/pull/136

The test_data.json was updated using Django 1.11 using the following commands:

python3 manage.py migrate
python3 manage.py loaddata pmaweb/fixtures/test_data.json
python3 manage.py dumpdata --natural-foreign --natural-primary -e sites -e contenttypes -e auth.Permission --indent 2 -o pmaweb/fixtures/test_data.json

Reference:

• https://docs.djangoproject.com/en/2.2/releases/2.0/#foreign-key-constraints-are-now-enabled-on-sqlite
• https://www.coderedcorp.com/blog/how-to-dump-your-django-database-and-load-it-into-/

[williamdes]

You might want to drop my sed commands from the workflow file

[codecov[bot]]

Codecov Report

Merging #157 (b1dd19f) into master (f6d69ec) will increase coverage by 0.14%. The diff coverage is 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #157 +/- ## ========================================== + Coverage 64.62% 64.77% +0.14% ========================================== Files 68 69 +1 Lines 1453 1459 +6 ========================================== + Hits 939 945 +6 Misses 514 514 ```