Bump coverage in /backend in the python-packages group

Bumps the python-packages group in /backend with 1 update: [coverage](https://github.com/nedbat/coveragepy).


Updates `coverage` 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
  dependency-group: python-packages
...

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

backend/requirements.txt

@@ -1,4 +1,4 @@
-coverage==7.6.7
+coverage==7.6.8
 Twisted==24.10.0
 psycopg2-binary==2.9.10
 pylint==3.3.1