Upgrade Redis Chart to version 7.x

Summary

From a thread during review of Bump redis-rb to version 5.0.8 (gitlab-org/build/CNG!1596 - merged)2

Do we functionally have a reason that we must have 7.x?

We bumped redis in GitLab Omnibus with Upgrade redis to version 7 (gitlab-org/omnibus-gitlab#7276 - closed) • Balasankar 'Balu' C • 16.2 • On track

It seems like .COM is using that version, though it's the clustered form: gitlab-org/omnibus-gitlab#7276 (comment 1456442895)

There were also some notes on performance increases in the rest of the notes for the linked Omnibus GitLab issue.

I will resolve this out to an issue and we can discuss further there, @WarheadsSE

Deliverables

1. Determine whether Charts should be upgraded to redis 7.x series
   • If we are upgrading, then determine how closely we can align to Omnibus GitLab and upgrade the Chart versions
   • If we are not upgrading, add a architecture decision record explaining why for future reference