Simplify the output in AfterPrint()

- Change FinishPrint() to AfterPrint()
  (As suggested in #31160)
- add a newline to separate it from the table
- remove the "objects" and ()
- assume plural

pkg/kubectl/cmd/cmd_test.go

@@ -166,7 +166,7 @@ func (t *testPrinter) HandledResources() []string {
 	return []string{}
 }
 
-func (t *testPrinter) FinishPrint(output io.Writer, res string) error {
+func (t *testPrinter) AfterPrint(output io.Writer, res string) error {
 	return nil
 }