[css-flexbox-1] Tweak wording in changelog.

Author: fantasai

css-flexbox-1/Overview.bs

@@ -3658,7 +3658,9 @@ Changes since the <a href="https://www.w3.org/TR/2018/CR-css-flexbox-1-20181119/
 			</blockquote>
 
 		<li id="change-2018-bracket-range-notation">
-			Changed syntax to use <a>CSS bracketed range notation</a> to reflect the prose restrictions on negative values.
+			Updated value syntax in property definition tables
+			to use newer <a>CSS bracketed range notation</a>
+			reflecting the prose restrictions on negative values.
 			(Editorial.)
 
 		<li id="change-2018-preferred-aspect-ratio">