[css-pseudo-4] Remove parenthetical #4500

Author: fantasai

css-pseudo-4/Overview.bs

@@ -320,7 +320,7 @@ Finding the First Letter</h4>
   Thus, in <code>&lt;DIV&gt;&lt;P STYLE="display: inline-block"&gt;Hello&lt;BR&gt;Goodbye&lt;/P&gt; etcetera&lt;/DIV&gt;</code>
   the first letter of the <code>DIV</code> is not the letter "H".
   In fact, the <code>DIV</code> doesn't have a first letter.
-  If an element is a list item (''display: list-item''),
+  If an element is a [=list item=]
   the ''::first-letter'' applies
   to the first letter in the principal box <em>after</em> the marker.
   User-Agents may ignore ''::first-letter''