Bump pytest from 6.1.2 to 6.2.1

Bumps [pytest](https://github.com/pytest-dev/pytest) from 6.1.2 to 6.2.1.
- [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/6.1.2...6.2.1)

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

requirements-dev.txt

@@ -1,7 +1,7 @@
 -e .
 flake8==3.8.4
 async-timeout==3.0.1
-pytest==6.1.2
+pytest==6.2.1
 pytest-cov==2.10.1
 pytest-mock==3.3.1
 coverage==5.3.1