Bump coverage from 5.5 to 6.0.2 (#363)

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.5 to 6.0.2.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.5...6.0.2)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

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

requirements-dev.txt

@@ -1,7 +1,7 @@
 -e .
 black==21.9b0
 bandit==1.7.0
-coverage==5.5
+coverage==6.0.2
 docutils==0.17.1
 flake8==3.9.2
 mypy==0.910