Bump django from 2.2.18 to 2.2.19

Bumps [django](https://github.com/django/django) from 2.2.18 to 2.2.19.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.2.18...2.2.19)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -1,5 +1,5 @@
 coverage==5.4
-Django==2.2.18
+Django==2.2.19
 django-debug-toolbar==3.2
 docutils==0.16
 freezegun==1.1.0