Stop using White_Space

For semantics of something being empty (table cells in this case) we should only consider ASCII whitespace, as we do elsewhere.

Fixes #4854.

source

@@ -4452,16 +4452,6 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
   <h4>Common parser idioms</h4>
 
-  </div>
-
-  <p>The <dfn data-x="White_Space">White_Space characters</dfn> are those that have the Unicode
-  property "White_Space" in the Unicode <code data-x="">PropList.txt</code> data file. <ref spec=UNICODE></p>
-
-  <p class="note">This is not to be confused with the "White_Space" value (abbreviated "WS") of the
-  "Bidi_Class" property in the <code data-x="">Unicode.txt</code> data file.</p>
-
-  <div w-nodev>
-
   <p>Some of the micro-parsers described below follow the pattern of having an <var>input</var>
   variable that holds the string being parsed, and having a <var>position</var> variable pointing at
   the next character to parse in <var>input</var>.</p>
@@ -42221,8 +42211,8 @@ interface <dfn>HTMLTableCellElement</dfn> : <span>HTMLElement</span> {
   data-x="attr-th-scope">scope</code> attribute is in the <span data-x="attr-th-scope-rowgroup">row
   group</span> state.</p>
 
-  <p>A cell is said to be an <dfn>empty cell</dfn> if it contains no elements and its text content,
-  if any, consists only of <span>White_Space</span> characters.</p>
+  <p>A cell is said to be an <dfn>empty cell</dfn> if it contains no elements and its <span>child
+  text content</span>, if any, consists only of <span>ASCII whitespace</span>.</p>
 
   </div>
 
@@ -124264,6 +124254,7 @@ INSERT INTERFACES HERE
   Mark Miller,
   Mark Nottingham,
   Mark Pilgrim,
+  Mark Rogers, <!-- dd8 on GitHub -->
   Mark Rowe<!--bdash-->,
   Mark Schenk,
   Mark Vickers,