[release-branch.go1.12] doc: document Go 1.12.17

Change-Id: I95f81f269e742ac058cb3e6404cc43beb2428926
Reviewed-on: https://go-review.googlesource.com/c/go/+/219200
Run-TryBot: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>

doc/devel/release.html

@@ -146,6 +146,12 @@ the <code>crypto/x509</code> package. See the
 1.12.16 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.12.17 (released 2020/02/12) includes a fix to the runtime. See
+the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.12.17+label%3ACherryPickApproved">Go
+1.12.17 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.11">go1.11 (released 2018/08/24)</h2>
 
 <p>