chore!: upgrade Django version to 4.2 (LTS)

This reverts commit 6f32d0e6f1.

.github/workflows/migrations-check.yml

@@ -16,16 +16,11 @@ jobs:
         os: [ ubuntu-20.04 ]
         python-version: [ 3.8 ]
         # 'pinned' is used to install the latest patch version of Django
-        # within the global constraint i.e. Django==3.2.21 in current case
+        # within the global constraint i.e. Django==4.2.8 in current case
         # because we have global constraint of Django<4.2 
-        django-version: ["pinned", "4.2"]
+        django-version: ["pinned"]
         mongo-version: ["4"]
-        mysql-version: ["5.7", "8"]
-        # excluding mysql5.7 with Django 4.2 since Django 4.2 has 
-        # dropped support for MySQL<8
-        exclude:
-          - django-version: "4.2"
-            mysql-version: "5.7"
+        mysql-version: ["8"]
     services:
       mongo:
         image: mongo:${{ matrix.mongo-version }}

.github/workflows/unit-tests.yml

@@ -17,7 +17,6 @@ jobs:
           - "3.8"
         django-version:
           - "pinned"
-          - "4.2"
         # When updating the shards, remember to make the same changes in
         # .github/workflows/unit-tests-gh-hosted.yml
         shard_name: