[x/blog] content/go1.15-proposals.article: revert "use relative links for other blog articles"
[x/blog] content/go1.15-proposals.article: revert "use relative links for other blog articles"

This reverts CL 216626 (commit 8bf1296992b6579acabcba62cc6cd0efe039c38a).

We cannot rely on relative links in blog posts to stay relative to
blog.golang.org, because blog posts are also embedded on golang.org.
This change caused those links to point to
https://golang.org/go2-here-we-come, which is 404.

Fixes golang/go#36930
Updates golang/go#36944

Change-Id: Ie5ca8f112ff6465328d258b283d540c07e909a54
Reviewed-on: https://go-review.googlesource.com/c/blog/+/217239
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
X-Blog-Commit: e1c854a5c639de192ed53c9fb8059c6be190b182

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