[Rules] Update index.mdx

[nenizera]

Hello team,

Summary

Can we link it to our webpage on Cloudflare plans?

https://www.cloudflare.com/en-gb/plans/

Thanks!

[pedrosousa]

I don't think we should link to the plans page here.

• If we were pointing to a specific plan, this could make sense. With the feature being available to everyone, it's less relevant and not the best place to promote our paid plans or differentiate them.
• We use the expression "available on all Cloudflare plans" often, and in other occurrences we don't have any link.