Editorial: make shape attributes table consistent

Helps with #9832.

source

@@ -41489,17 +41489,14 @@ interface <dfn interface>HTMLAreaElement</dfn> : <span>HTMLElement</span> {
   data-x="attr-area-coords">coords</code> attributes specify the area.</p>
 
   <p>The <dfn element-attr for="area"><code data-x="attr-area-shape">shape</code></dfn> attribute is
-  an <span>enumerated attribute</span>. The following table lists the keywords defined for this
-  attribute. The states given in the first cell of the rows with keywords give the states to which
-  those keywords map.  <span w-nodev>Some of the keywords are non-conforming, as noted in the last
-  column.</span></p>
+  an <span>enumerated attribute</span> with the following keywords and states:</p>
 
   <table>
    <thead>
     <tr>
      <th>State
      <th>Keywords
-     <th w-nodev>Notes
+     <th w-nodev>Brief description
    <tbody>
     <tr>
      <td w-nodev rowspan=2><span data-x="attr-area-shape-circle">Circle state</span>
@@ -41531,8 +41528,8 @@ interface <dfn interface>HTMLAreaElement</dfn> : <span>HTMLElement</span> {
      <td w-nodev>Non-conforming
   </table>
 
-  <p>The attribute may be omitted. The <i data-x="missing value default">missing value default</i>
-  and <i data-x="invalid value default">invalid value default</i> are the <span
+  <p>The attribute's <i data-x="missing value default">missing value default</i> and <i
+  data-x="invalid value default">invalid value default</i> are both the <span
   data-x="attr-area-shape-rect">rectangle</span> state.</p>
 
   <p>The <dfn element-attr for="area"><code data-x="attr-area-coords">coords</code></dfn> attribute