Bump pytest-cov from 2.11.1 to 2.12.0 (#216)

Bumps [pytest-cov](https://github.com/pytest-dev/pytest-cov) from 2.11.1 to 2.12.0.
- [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@v2.11.1...v2.12.0)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_test.txt

@@ -1,4 +1,4 @@
 pytest==6.2.4
 pytest-aiohttp==0.3.0
-pytest-cov==2.11.1
+pytest-cov==2.12.0
 pytest-timeout==1.4.2