docs: validating webhook policies to limit number of replicas

[Tomer20]

Added examples of ValidatingAdmissionPolicy to fail/deny ScaledObjects based on maxReplicaCount.

Checklist

• [x] Commits are signed with Developer Certificate of Origin (DCO)

Fixes #

[github-actions[bot]]

Thank you for your contribution! 🙏 We will review your PR as soon as possible.

While you are waiting, make sure to:

• Add your contribution to all applicable KEDA versions
• GitHub checks are passing
• Is the DCO check failing? Here is how you can fix DCO issues

Learn more about:

• How to become a listed end-user or a listed commerical offering
• Our contribution guide

[netlify[bot]]

✅ Deploy Preview for keda ready!

Name	Link
🔨 Latest commit	ee00cc135240e969e89eece56cf47ec38d8a18f9
🔍 Latest deploy log	https://app.netlify.com/sites/keda/deploys/66ef9b6ad576c10008940cf4
😎 Deploy Preview	https://deploy-preview-1471--keda.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[Tomer20]

Thanks!

Could you please also add similar change to version 2.16?

Thanks for the feedback @zroubalik. I added the docs for v2.16 as well.