Update pytest from 5.3.0 to 5.3.1 (#742)

Author: pyup-bot

requirements/requirements-testing.txt

@@ -1,7 +1,7 @@
 django-debug-toolbar==2.1
 factory-boy==2.12.0
 Faker==2.0.4
-pytest==5.3.0
+pytest==5.3.1
 pytest-cov==2.8.1
 pytest-django==3.7.0
 pytest-factoryboy==2.0.3