Update K8s version support

[realjoshparker]

Issue

N/A

Description

Update the version support docs so v2.0.0~v2.1.3 ends support on v1.21 of K8s. The current state of the docs indicate that these versions of the controller support K8s v1.15+ which is incorrect as they rely on the networking.k8s.io/v1beta1 API, which was removed in K8s v1.22. Below is a few log lines from my v1.32 cluster confirming v2.1.3 of the controller is using the removed API version

{"level":"info","ts":1752608955.1141255,"msg":"version","GitVersion":"v2.1.3","GitCommit":"c9d30f23960f12cd1e985e9b2cd3f077b9a8c93f","BuildDate":"2021-02-18T19:32:05+0000"}
{"level":"info","ts":1752608955.1508875,"logger":"controller-runtime.metrics","msg":"metrics server is starting to listen","addr":":8080"}
{"level":"error","ts":1752608955.1711683,"logger":"setup","msg":"unable to create controller","controller":"Ingress","error":"no matches for kind \"Ingress\" in version \"networking.k8s.io/v1beta1\""}

Further according to this comment on issue #2495 support for the GA version of this API wasn't added until v2.4.0 of the controller and therefore this should have a similar end of support for v1.21 of K8s like the v2.2.0~v2.3.1 versions.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: realjoshparker / name: Josh Parker (7a5f2a0)

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @realjoshparker. Thanks for your PR.

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[zac-nixon]

/lgtm
/approved

thanks for doing this!

[zac-nixon]

/retest

[realjoshparker]

/retest

[k8s-ci-robot]

@realjoshparker: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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