Update go-redis dependency to support redis v7+

[oleiade]

Users recently encountered issues linked to the version of go-redis we use, especially when it comes to cluster mode. We should switch the go-redis dependency to its latest major version.

First experiments around this outlined that some of our tests might break because of that change. I believe there were changes in the protocol in redis between version 6 and 7, and those would need to be addressed on our part.