Update docs for 3scale WebAssembly integration

From Jamie's email:

...the tech preview of Kuadrant is what the 3Scale team have been working toward, and checking the last update from them, their action item was to create a blog post on using Kuadrant with OSSM. I didn't think it'd be worth updating the doc page while Kuadrant before they write the blog post at least (a bit like Kiali's console integration). I'll follow up with them...

Claire/Tim/Robert: The title "3scale WebAssembly for 2.1" is a little unfortunate, as it should probably be "...2.1+. As we no longer support Service Mesh 2.0 though, perhaps the "3Scale Istio Adapter for 2.0" can be removed? Then the other title could simply be "3Scale Integration". Eventually, we'll want to evolve that page as Kuadrant develops...

Acceptance Criteria:

• Determine if 3Scale Istio Adapter for 2.0 can be removed, and update doc if appropriate
• Change remaining section title to "3Scale Integration" (applies to all versions of OSSM now)