doc/go1.18: add changes to strconv.Unquote to release notes

CL 343877

Updates #47694

Change-Id: I37a0a0d1f7ab937b12812981ecddc89eb8c99c24
Reviewed-on: https://go-review.googlesource.com/c/go/+/368796
Trust: Jeremy Faller <[email protected]>
Run-TryBot: Jeremy Faller <[email protected]>
Reviewed-by: Joe Tsai <[email protected]>

Author: jeremyfaller

doc/go1.18.html

@@ -705,7 +705,8 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
 <dl id="strconv"><dt><a href="/pkg/strconv/">strconv</a></dt>
   <dd>
     <p><!-- CL 343877 -->
-      TODO: <a href="https://golang.org/cl/343877">https://golang.org/cl/343877</a>: reject surrogate halves in Unquote
+      <a href="/pkg/strconv/#strconv.Unquote"><code>strconv.Unquote</code></a>
+      now rejects Unicode surrogate halves.
     </p>
   </dd>
 </dl><!-- strconv -->