Update pytest requirement from <5.4 to <6.3

Updates the requirements on [pytest](https://github.com/pytest-dev/pytest) to permit the latest version.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@1.0.0b3...6.2.2)

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

setup.py

@@ -27,7 +27,7 @@
         'jsonschema==3.0.2', 'gunicorn'
     ],
     extras_require={
-        'test': ['coverage', 'pytest<5.4', 'pytest-cov',
+        'test': ['coverage', 'pytest<6.3', 'pytest-cov',
                  'coveralls', 'testfixtures', 'tox',
                  'flake8', 'flake8-docstrings', 'asynctest', 'aioresponses'],
         'docs': [