[x/blog] content: documented godoc's "Deprecated:" convention in the godoc post
[x/blog] content: documented godoc's "Deprecated:" convention in the godoc post

Fixes golang/go#10909

Change-Id: Ie2553bc2f6983cbcaf7398366c21dc175e1f5453
Reviewed-on: https://go-review.googlesource.com/18956
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>
X-Blog-Commit: 257114af91a0defb1fc2c16c7f4ae2429b8a4e0f

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