Bump coverage from 7.6.7 to 7.6.8

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:production
  update-type: version-update:semver-patch
...

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

requirements-testing.txt

@@ -1,6 +1,6 @@
 colorama==0.4.6
 coverage==7.6.1; python_version<="3.8"
-coverage==7.6.7; python_version>="3.9"
+coverage==7.6.8; python_version>="3.9"
 green==4.0.2
 lxml==5.3.0
 parameterized==0.9.0