docs: fix Redis wording in README

[ansn366]

Summary

• Use consistent Redis capitalization in the README
• Clarify that the library supports multiple Redis versions

Verification

• Reviewed the Markdown diff

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Note

Low Risk
Documentation-only wording tweaks in README.md with no code or behavior changes.

Overview
Fixes README wording so Redis and Docker are capitalized consistently, and so the supported-versions sentence refers to multiple Redis versions rather than a single “version.”

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[ggivo]

Thanks for spotting it,
We are planning a beta/patch release that will include it, along with an update to the release preparation steps.