build(deps): update coverage requirement from ==7.6.* to ==7.7.* in /requirements (#378)

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/7.6.0...7.7.1)

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

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