doc/go1.20: delete remaining TODO

This section is complete.

For #54202.

Change-Id: I304cc55a5b8ed53e8b8dff73a5feb5ef39207846
Reviewed-on: https://go-review.googlesource.com/c/go/+/455895
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

doc/go1.20.html

@@ -522,10 +522,6 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
   There are also various performance improvements, not enumerated here.
 </p>
 
-<p>
-  TODO: complete this section
-</p>
-
 <dl id="archive/tar"><dt><a href="/pkg/archive/tar/">archive/tar</a></dt>
   <dd>
     <p><!-- https://go.dev/issue/55356, CL 449937 -->