cmd/server: use redis=~5.0

Created by: bobheadxi

The redis release we depend on for this image got pulled: https://pkgs.alpinelinux.org/packages?name=redis&branch=v3.12 This is currently causing persistent build failures in main.

This PR makes the constraint looser so that we can pull the dependency at least, which comes with the unfortunate tradeoff that we cannot pin the version, but we also found the following:

Unfortunately, Alpine-Linux Package Management drops older packages when there are newer versions available. This makes it hard to use Alpine Linux with docker since you want a reproducible image with exact versions.

https://superuser.com/questions/1174021/why-does-alpine-apk-report-unsatisfiable-constraints-when-installing-an-older/1486407#1486407

You should avoid being explicit on package versions unless controlling your own package mirror and package builds, rather allow the package system to handle it for the Alpine release in use.

https://superuser.com/questions/1174021/why-does-alpine-apk-report-unsatisfiable-constraints-when-installing-an-older

Perhaps we shouldn't be pinning any of these dependencies 🤔