doc/go1.19: add pdqsort change to release notes

Change-Id: I4a36491e561f3b2112f980ff580fa4f85d501b6a
Reviewed-on: https://go-review.googlesource.com/c/go/+/408834
Auto-Submit: Eli Bendersky‎ <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Eli Bendersky‎ <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Eli Bendersky <[email protected]>

Author: eliben

doc/go1.19.html

@@ -350,7 +350,9 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
 <dl id="sort"><dt><a href="/pkg/sort/">sort</a></dt>
   <dd>
     <p><!-- CL 371574 -->
-      TODO: <a href="https://go.dev/cl/371574">https://go.dev/cl/371574</a>: use pdqsort
+      The sorting algorithm has been rewritten to use
+      <a href="https://arxiv.org/pdf/2106.05123.pdf">pattern-defeating quicksort</a>, which
+      is faster for several common scenarios.
     </p>
   </dd>
 </dl><!-- sort -->