Updating deprecation statement for Service Mesh Extension API

Update the Extensions Assembly

Update FOUR notes in the assembly that mention the deprecation, and the introductory text in the https://docs.openshift.com/container-platform/4.11/service_mesh/v2x/ossm-extensions.html#ossm-extensions-migration-overview_ossm-extensions topic.

Change "'The ServiceMeshExtension API is deprecated as of Red Hat OpenShift Service Mesh version 2.2 and will be removed in a future release. " to 'The ServiceMeshExtension API is deprecated as of Red Hat OpenShift Service Mesh version 2.2 and was removed as of Red Hat OpenShift Service Mesh version 2.3 . "

remove references to wasm-cacher

wasm-cacher is a pod that's deployed as part of the OSSM 2.x. It's part of the ServiceMeshExtension implementation. In 2.3 we don't support SME anymore, and this component was removed from the control plane

It resides in three places:

$ git grep wasm-cacher
modules/ossm-control-plane-cli.adoc:wasm-cacher-basic-8c986c75-vj2cd 1/1 Running 0 65m
modules/ossm-validating-smcp.adoc:** `wasm-cacher`
modules/ossm-validating-smcp.adoc:wasm-cacher-basic-5b99bfcddb-m775l 1/1 Running 0 86s