chore(deps-dev): bump coverage from 7.6.7 to 7.6.8 in /requirements

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
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements/dev.txt

@@ -1,6 +1,6 @@
 -r pre-dev.txt
 
-coverage==7.6.7; python_version>="3.9"
+coverage==7.6.8; python_version>="3.9"
 coverage==7.6.1; python_version<"3.9"
 pytest-cov==6.0.0; python_version>="3.9"
 pytest-cov==5.0.0; python_version<"3.9"