Remove unstructured error checking from affected code

Also remove error messages that depended on ObjectKinds() - future
changes will potentially remove this interface and the replacements here
are equivalent.

pkg/kubectl/cmd/apply_set_last_applied.go

@@ -112,7 +112,7 @@ func (o *SetLastAppliedOptions) Complete(f cmdutil.Factory, cmd *cobra.Command)
 	o.Codec = f.JSONEncoder()
 
 	var err error
-	o.Mapper, o.Typer, err = f.UnstructuredObject()
+	o.Mapper, o.Typer = f.UnstructuredObject()
 	if err != nil {
 		return err
 	}