Update supported Kubernetes versions to include 1.26

What does this MR do and why?

Kubernetes 1.26 was released on 9 December 2022, and we have ensured that our projects support this new version. See #385388 (comment 1226419919)

This MR updates the documentation around the Kubernetes versions we are supporting. The date is based on the fact that Kubernetes has a 4-month release cycle, which means that 1.29 would likely be released in December 2023. We have given ourselves 3 months to support a new Kubernetes version, so that would mean we'll start supporting 1.29 on March 2024 and stop supporting 1.26 on the same date.

Issue: #385388 (closed) | Epic: &9458 (closed)

Screenshots or screen recordings

N/A

How to set up and validate locally

N/A

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.