doc: document Go 1.11.7

Change-Id: Iec5e69b3ea163f42234d3b73696427a7aa8732e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/170884Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/devel/release.html

@@ -106,6 +106,13 @@ runtime, go command, and the <code>crypto/x509</code>, <code>encoding/json</code
 1.11.6 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.11.7 (released 2019/04/05) includes fixes to the runtime and the
+<code>net</code> packages. See the
+<a href="https://github.com/golang/go/issues?q=milestone%3AGo1.11.7">Go
+1.11.7 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.10">go1.10 (released 2018/02/16)</h2>
 
 <p>