Bump pytest-cov from 2.8.1 to 2.9.0

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.8.1 to 2.9.0.
- [Release notes](https://github.com/pytest-dev/pytest-cov/releases)
- [Changelog](https://github.com/pytest-dev/pytest-cov/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest-cov@v2.8.1...v2.9.0)

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

test-requirements.txt

@@ -34,7 +34,7 @@ py==1.8.1                 # via pytest
 pyparsing==2.4.7          # via packaging
 pytest-aiohttp==0.3.0     # via -r test-requirements.in
 pytest-asyncio==0.12.0    # via -r test-requirements.in
-pytest-cov==2.8.1         # via -r test-requirements.in
+pytest-cov==2.9.0         # via -r test-requirements.in
 pytest-django==3.9.0      # via -r test-requirements.in
 pytest-mock==3.1.0        # via -r test-requirements.in
 pytest-mypy==0.6.2        # via -r test-requirements.in