Mark Redis cache backend options as deprecated

[56quarters]

Which issue(s) this PR fixes or relates to

Part of https://github.com/grafana/mimir-squad/issues/2414

Related #9441

Checklist

• [ ] Tests updated.
• [X] Documentation added.
• [ ] CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• [ ] about-versioning.md updated with experimental features.

[56quarters]

🔥 Thank you for collecting the list. We can backport it to release-2.14 after.

(nit) Shall we changelog it?

Sure, I'll add a changelog entry. This PR was originally opened against the release branch but I'll change to main and we can backport to the release branch.

[grafanabot]

The backport to release-2.14 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-9453-to-release-2.14 origin/release-2.14
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x d435e78bf54c3ee12c14490334114cbc3ce4aaec
# Push it to GitHub
git push --set-upstream origin backport-9453-to-release-2.14
git switch main
# Remove the local backport branch
git branch -D backport-9453-to-release-2.14

Then, create a pull request where the base branch is release-2.14 and the compare/head branch is backport-9453-to-release-2.14.