doc: update 1.9.3 release date

Change-Id: I689ccfb8452a170629425dc97da503b28766c6f9
Reviewed-on: https://go-review.googlesource.com/89035Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/devel/release.html

@@ -50,7 +50,7 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.9.2">Go
 </p>
 
 <p>
-go1.9.3 (released 2018/01/19) includes fixes to the compiler, runtime,
+go1.9.3 (released 2018/01/22) includes fixes to the compiler, runtime,
 and the <code>database/sql</code>, <code>math/big</code>, <code>net/http</code>,
 and <code>net/url</code> packages.
 See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.9.3">Go