doc/go1.18: remove some TODOs for changes we aren't mentioning again

These TODOs were originally removed in CL 368794.

Updates #47694

Change-Id: I39d5c0ce5f96adbbc466585a5831f721057dbed5
Reviewed-on: https://go-review.googlesource.com/c/go/+/384619
Trust: Carlos Amedee <[email protected]>
Run-TryBot: Carlos Amedee <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: cagedmantis

doc/go1.18.html

@@ -1074,15 +1074,7 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
       The old names will continue to work, but will be deprecated in a
       future Go release.
     </p>
-
-    <p><!-- CL 321889 -->
-      TODO: <a href="https://golang.org/cl/321889">https://golang.org/cl/321889</a>: allocate hiter as part of MapIter
-    </p>
-
-    <p><!-- CL 345486 -->
-      TODO: <a href="https://golang.org/cl/345486">https://golang.org/cl/345486</a>: optimize for maps with string keys
-    </p>
-  </dd>
+  </dd><!-- CL 321889 and CL 345486 are optimizations, no need to mention. -->
 </dl><!-- reflect -->
 
 <dl id="regexp"><dt><a href="/pkg/regexp/">regexp</a></dt>