doc/go1.16: address some remaining high-level TODOs

The tools section TODO can be removed since the tools section looks
complete by now.

All TODOs in the minor changes to the library section have been done,
so the top-level TODO is resolved. Delete it.

The currently highlighted entries under Core library section look
good. It's worth reviewing this further based on feedback from Go
1.16 pre-releases, so keep the TODO but make it non-user-visible
to unblock Go 1.16 Beta 1.

For #40700.

Change-Id: Ie72661bd457b0a93ef92e1bfc0844072f3b618a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/277212
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.16.html

@@ -99,10 +99,6 @@ Do not send CLs removing the interior tags from such phrases.
 
 <h2 id="tools">Tools</h2>
 
-<p>
-  TODO
-</p>
-
 <h3 id="go-command">Go command</h3>
 
 <h4 id="modules">Modules</h4>
@@ -438,10 +434,10 @@ Do not send CLs removing the interior tags from such phrases.
   implementations.
 </p>
 
-<p>
-  TODO: when the "Minor changes to the library" section is close to completion,
-  decide if any changes are worth factoring out and highlighting in "Core library"
-</p>
+<!-- okay-after-beta1
+  TODO: decide if any additional changes are worth factoring out from
+  "Minor changes to the library" and highlighting in "Core library"
+-->
 
 <h3 id="minor_library_changes">Minor changes to the library</h3>
 
@@ -451,10 +447,6 @@ Do not send CLs removing the interior tags from such phrases.
   in mind.
 </p>
 
-<p>
-  TODO: complete this section, resolve TODOs below, add missing entries
-</p>
-
 <dl id="crypto/dsa"><dt><a href="/pkg/crypto/dsa/">crypto/dsa</a></dt>
   <dd>
     <p><!-- CL 257939 -->