doc/go1.19: fix HTML validation issues

Avoid duplicating tag ID runtime and remove a superflous </dd> tag.

Found by https://validator.w3.org

Change-Id: I9c84b8257acbb6d3d6817192bb8d355207944b9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/413254
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>

Author: tklauser

doc/go1.19.html

@@ -741,7 +741,7 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
   </dd>
 </dl><!-- regexp -->
 
-<dl id="runtime"><dt><a href="/pkg/runtime/">runtime</a></dt>
+<dl id="pkg-runtime"><dt><a href="/pkg/runtime/">runtime</a></dt>
   <dd>
     <p><!-- https://go.dev/issue/51461 -->
       The <a href="/pkg/runtime/#GOROOT"><code>GOROOT</code></a> function now returns the empty string
@@ -847,7 +847,6 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
       but often easier to use: it returns an additional boolean reporting whether an equal value was found.
     </p>
   </dd>
-  </dd>
 </dl><!-- sort -->
 
 <dl id="strconv"><dt><a href="/pkg/strconv/">strconv</a></dt>