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/custom_column_printer.go

@@ -155,7 +155,7 @@ type CustomColumnsPrinter struct {
 	NoHeaders bool
 }
 
-func (s *CustomColumnsPrinter) FinishPrint(w io.Writer, res string) error {
+func (s *CustomColumnsPrinter) AfterPrint(w io.Writer, res string) error {
 	return nil
 }