[deps] Update redis requirement from ~=5.0.7 to ~=5.0.8

Updates the requirements on [redis](https://github.com/redis/redis-py) to permit the latest version.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v5.0.7...v5.0.8)

---
updated-dependencies:
- dependency-name: redis
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Federico Capoano <[email protected]>

requirements-test.txt

@@ -6,5 +6,5 @@ freezegun~=1.5.1
 openwisp-monitoring @ https://github.com/openwisp/openwisp-monitoring/tarball/master
 openwisp-controller @ https://github.com/openwisp/openwisp-controller/tarball/master
 openwisp-utils[qa,selenium] @ https://github.com/openwisp/openwisp-utils/tarball/master
-redis~=5.0.7
+redis~=5.0.8
 django_redis~=5.2.0