content/9years: drop explicit height from image directives

The images are stretched on mobile (but not desktop).
Dropping the explicit width fixes the problem.
Not sure why, but it does.

Change-Id: I580188dc0d7a96ced1a4777988878a58f59b127d
Reviewed-on: https://go-review.googlesource.com/c/148886
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/content/9years.article b/content/9years.article
index ccd714b..ca7fd1d 100644
--- a/content/9years.article
+++ b/content/9years.article
@@ -56,7 +56,7 @@
 The Go community is truly global.
 At GopherCon Europe in Iceland this past summer, gophers literally spanned the gap between the continents.
 
-.image 9years-iceland.jpg 338 800
+.image 9years-iceland.jpg _ 800
 
 _(Photo_by_Winter_Francia.)_
 
@@ -84,7 +84,7 @@
 The project hit a major milestone in Q2 2018 when, for the first time,
 we had more contributions coming from the community than the Go team.
 
-.image 9years-graph.png 371 600
+.image 9years-graph.png _ 600
 
 * Thank You