[css-cascade-4] Replace @import supports() example (#8594)

Author: CanadaHonk

css-cascade-4/Overview.bs

@@ -221,14 +221,14 @@ Conditional ''@import'' Rules</h3>
 	(even if it is loaded through some other link).
 
 	<div class="example">
-		The following rule illustrates how an author can provide fallback rules for legacy user agents
-		without impacting network performance on newer user agents:
+		The following rule illustrates how an author can provide rules
+		for modern user agents that support newer web features 
+		without impacting network performance on older user agents.
+		In this example, a CSS file which loads COLRv1 fonts
+		is only fetched when COLRv1 is supported:
 
 		<pre class='lang-css'>
-		@import url("fallback-layout.css") supports(not (display: flex));
-		@supports (display: flex) {
-		  ...
-		}
+		@import url("COLRv1_fonts.css") supports(font-tech(color-COLRv1));
 		</pre>
 	</div>