chore(deps): bump coverage from 4.5.4 to 6.4.4 in /dev_requirements

Bumps [coverage](https://github.com/nedbat/coveragepy) from 4.5.4 to 6.4.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](coveragepy/coveragepy@coverage-4.5.4...6.4.4)

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

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

Author: dependabot[bot]

dev_requirements/coverage-requirements.txt

@@ -1,4 +1,4 @@
-coverage==4.5.4
+coverage==6.4.4
 mypy==0.971
 mypy-extensions==0.4.3
 typing==3.7.4.3