doc: remove link to empty Go 1.5.3 milestone

Fixes #14687

Change-Id: I51fd8842d35c82db71cc5b28c4c0550871461eb6
Reviewed-on: https://go-review.googlesource.com/20421Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/devel/release.html

@@ -65,8 +65,7 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.5.2">Go
 <p>
 go1.5.3 (released 2016/01/13) includes a security fix to the <code>math/big</code> package
 affecting the <code>crypto/tls</code> package.
-See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.5.3">Go 1.5.3 milestone on our issue tracker</a>
-and the <a href="https://golang.org/s/go153announce">release announcement</a> for details.
+See the <a href="https://golang.org/s/go153announce">release announcement</a> for details.
 </p>
 
 <h2 id="go1.4">go1.4 (released 2014/12/10)</h2>