Remove reference to plugin component since it's removed for time being

Author: sleshchenko

docs/modules/user-guide/pages/adding-plugin-component-to-a-devfile.adoc

@@ -15,9 +15,8 @@ Each component in a single devfile must have a unique name.
 
 . For each component, define an unique value for the mandatory `name` attribute.
 
-. For each component, define a mandatory type of one of the following types: `plugin`, `kubernetes` or `container`.
+. For each component, define a mandatory type of one of the following types: `kubernetes`, `container` or `volume`.
 
-. xref:adding-plugin-component-to-a-devfile.adoc[]
 . xref:adding-kubernetes-component-to-a-devfile.adoc[]
 . xref:adding-container-component-to-a-devfile.adoc[]
 . xref:specifying-persistent-storage.adoc[]

docs/modules/user-guide/partials/proc_adding-components-to-a-devfile.adoc

@@ -8,7 +8,7 @@ This section describes how to migrate components to v2.x devfiles. A component s
 
 . Component is a polymorphic type
 +
-The validation component is now defined as a polymorphic type and can be implemented as `container`, `kubernetes`, `openshift`, `plugin`, or `volume`.
+The validation component is now defined as a polymorphic type and can be implemented as `container`, `kubernetes`, `openshift`, or `volume`.
 +
 [source,yaml]
 ----