[css-inline-3] Simplify grammar using required multiplier.

Author: fantasai

css-inline-3/Overview.bs

@@ -1747,7 +1747,7 @@ Alignment of Initial Letters: the 'initial-letter-align' property</h3>
 
 	<pre class="propdef" id="initial-letter-align">
 	Name: <dfn id="propdef-initial-letter-align">initial-letter-align</dfn>
-	Value: border-box? [ alphabetic | ideographic | hebrew | hanging ] | border-box
+	Value: [ border-box? [ alphabetic | ideographic | hebrew | hanging ]? ]!
 	Initial: alphabetic
 	Applies to: certain inline-level boxes and <css>::first-letter</css> and inside <css>::marker</css> boxes (<a href="#first-most-inline-level">see prose</a>)
 	Inherited: yes