poetry bot: bump coverage from 7.6.1 to 7.6.4

Bumps [coverage](https://github.com/nedbat/coveragepy) from 7.6.1 to 7.6.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@7.6.1...7.6.4)

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

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