doc/go1.16: add crypto/tls Config.Clone note

For #40700
Fixes #42896

Change-Id: I842c9d60b18abe2ee061c6705a5c7ba62b224d77
Reviewed-on: https://go-review.googlesource.com/c/go/+/274613
Trust: Roland Shoemaker <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: rolandshoemaker

doc/go1.16.html

@@ -405,7 +405,8 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
     </p>
 
     <p><!-- CL 246637 -->
-      TODO: <a href="https://golang.org/cl/246637">https://golang.org/cl/246637</a>: make config.Clone return nil if the source is nil
+      <a href="/pkg/crypto/tls/#Config.Clone"><code>Config.Clone</code></a> now returns
+      a nil <code>*Config</code> if the source is nil, rather than panicking.
     </p>
   </dd>
 </dl><!-- crypto/tls -->