build(deps): update coverage requirement from ==7.8.* to ==7.9.* in /requirements (#409)

build(deps): update coverage requirement in /requirements

Updates the requirements on [coverage](https://github.com/nedbat/coveragepy) to permit the latest version.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](https://github.com/nedbat/coveragepy/compare/7.8.0...7.9.1)

---
updated-dependencies:
- dependency-name: coverage
  dependency-version: 7.9.1
  dependency-type: direct:production
...

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