[x/blog] content/constants.article: fix typo
[x/blog] content/constants.article: fix typo

Delete duplicate "has".

Change-Id: I7f21b4347702962f7ac2f26c235eae642b290166
Reviewed-on: https://go-review.googlesource.com/23553
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>
X-Blog-Commit: 8b16845fc1df744688a021c727a11ec4a3a390b4

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