feat(cache): add valkey and valkeys as allowed schemes

[Zerotask]

This PR adds the alternative schemes valkey and valkeys, which is also the recommendation from django-valkey.

Fixes #553

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Valkey is an open source drop-in replacement for Redis:

This project was forked from the open source Redis project right before the transition to their new source available licenses.
(https://github.com/valkey-io/valkey)

https://django-valkey.readthedocs.io/en/latest/configure/advanced_configurations.html

[github-actions]

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