Plugin user guides need to be updated for recent releases

[aimeeu]

From Ryan Pei at Armory: OSS docs have the latest config noted as a v1.23+ change (https://spinnaker.io/guides/user/plugins/#plugin-v2-configuration-changes). Wonder if we should make this the default config in both the OSS and Armory docs and move the old way of configuring plugins to a "Note: If you are on an older version..." section