[release-branch.go1.11] doc: document Go 1.11.9

Updates #31293

Change-Id: I3d72f732be7b28059310ea6fc134c3bfac81492d
Reviewed-on: https://go-review.googlesource.com/c/go/+/171578
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
(cherry picked from commit ab2a0803383f0f019db0b2252095f2fdb7735cea)
Reviewed-on: https://go-review.googlesource.com/c/go/+/171767
Reviewed-by: Bryan C. Mills <bcmills@google.com>
diff --git a/doc/devel/release.html b/doc/devel/release.html
index 6d6e2615..2fc9efa 100644
--- a/doc/devel/release.html
+++ b/doc/devel/release.html
@@ -89,7 +89,13 @@
 </p>
 
 <p>
-go1.11.8 (released 2019/04/08) fixes an issue where using the prebuilt binary
+go1.11.8 (released 2019/04/08) was accidentally released without its
+intended fix. It is identical to go1.11.7, except for its version
+number. The intended fix is in go1.11.9.
+</p>
+
+<p>
+go1.11.9 (released 2019/04/11) fixes an issue where using the prebuilt binary
 releases on older versions of GNU/Linux
 <a href="https://golang.org/issues/31293">led to failures</a>
 when linking programs that used cgo.