Bump pytest in /{{cookiecutter.app_name}}/requirements

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.3.0 to 5.3.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/5.3.0...5.3.1)

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

{{cookiecutter.app_name}}/requirements/dev.txt

@@ -2,7 +2,7 @@
 -r prod.txt
 
 # Testing
-pytest==5.3.0
+pytest==5.3.1
 WebTest==2.0.33
 factory-boy==2.12.0
 pdbpp==0.10.2