Bump the dev-deps group across 1 directory with 3 updates

Bumps the dev-deps group with 3 updates in the /backend directory: [coverage](https://github.com/nedbat/coveragepy), [virtualenv](https://github.com/pypa/virtualenv) and [pytest](https://github.com/pytest-dev/pytest).


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)

Updates `virtualenv` from 20.27.1 to 20.28.0
- [Release notes](https://github.com/pypa/virtualenv/releases)
- [Changelog](https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst)
- [Commits](pypa/virtualenv@20.27.1...20.28.0)

Updates `pytest` from 8.3.3 to 8.3.4
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.3.3...8.3.4)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: dev-deps
- dependency-name: virtualenv
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: dev-deps
- dependency-name: pytest
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: dev-deps
...

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