Bump coverage from 5.5 to 6.1.1 (#33)

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.5 to 6.1.1.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.5...6.1.1)

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

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

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

requirements.txt

@@ -1,4 +1,4 @@
-coverage==5.5
+coverage==6.1.1
 httptest==0.0.17
 mock==4.0.3
 pid==3.0.4