blog: fix dead links on go fmt blog post

Fix some links which no longer resolve on the post
introducing go fmt

Fixes golang/go#19036

Change-Id: I921eacd8b2ab55dbae7738e4a08b7819bda80576
Reviewed-on: https://go-review.googlesource.com/37191
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed