content/moretypes.article: 重新翻译 slice 练习
content/moretypes.article: 重新翻译 slice 练习

Fixes #211.

Signed-off-by: Minux <72d850dbd8858b791995463d8539b5a379577f28@golang.org>

Go-zh/tour,Go-zh/tour,Go-zh/tour,Go-zh/tour