Bump coverage from 7.6.7 to 7.6.8 (#1720)

Bumps [coverage](https://github.com/nedbat/coveragepy) from 7.6.7 to 7.6.8.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@7.6.7...7.6.8)

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

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