[css-color-4] update changes

Author: svgeesus

css-color-4/Overview.bs

@@ -4957,6 +4957,8 @@ Changes</h2>
 
 <ul>
 	<li>Defined the term host syntax</li>
+	<li>Added a new pair of system colors</li>
+	<li>Replaced table of HSL values with error-free version</li>
 	<!-- to 9 July 2021 -->
 	<li>Added Lea Verou as co-editor by WG resolution</li>
 	<li>Clarified that hue angle is unbounded</li>