Update pytest-cov from 2.12.1 to 3.0.0

Author: pyup-bot

requirements/requirements-testing.txt

@@ -2,7 +2,7 @@ django-debug-toolbar==3.2.2
 factory-boy==3.2.0
 Faker==8.14.1
 pytest==6.2.5
-pytest-cov==2.12.1
+pytest-cov==3.0.0
 pytest-django==4.4.0
 pytest-factoryboy==2.1.0
 snapshottest==0.6.0