[css-box-4] Fixup the changes section

Author: frivoal

css-box-4/Overview.bs

@@ -551,7 +551,6 @@ Changes Since CSS Level 3 {#changes}
 	since <a href="https://www.w3.org/TR/css-box-3/">Level 3</a>:
 	<ul>
 		<li>Adding the 'margin-trim' property.
-		<li>Adapting the prose slightly to account for vertical <a>writing modes</a>.
 	</ul>
 
 Changes Since CSS Level 2 {#changes}
@@ -560,7 +559,6 @@ Changes Since CSS Level 2 {#changes}
 	The following changes have been made to this module
 	since <a href="https://www.w3.org/TR/CSS2/box.html">Level 2</a>:
 	<ul>
-		<li>Adding the 'margin-trim' property.
 		<li>Adapting the prose slightly to account for vertical <a>writing modes</a>.
 	</ul>