[x/blog] go.blog: small fixes to slices article
[x/blog] go.blog: small fixes to slices article

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/8402043
X-Blog-Commit: 493d984eb4b5e38529742c05235c1c6a87982632

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website