build(deps-dev): bump coverage from 5.5 to 6.0.1 in /requirements

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.5 to 6.0.1.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.5...6.0.1)

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

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

requirements/requirements-ci.txt

@@ -139,7 +139,7 @@ constantly==15.1.0
     # via
     #   -r requirements-dev.txt
     #   twisted
-coverage==5.5
+coverage==6.0.1
     # via -r requirements-dev.txt
 cryptography==3.4.7
     # via

requirements/requirements-dev.txt

@@ -120,7 +120,7 @@ colour==0.1.5
     # via -r requirements-dev.in
 constantly==15.1.0
     # via twisted
-coverage==5.5
+coverage==6.0.1
     # via -r requirements-dev.in
 cryptography==3.4.7
     # via