[css-values-4] Rephrase the utf-8 URL-encoding requirement. #9301

Author: tabatkins

css-values-4/Overview.bs

@@ -1127,15 +1127,12 @@ URL Processing Model</h4>
 			with [=fetch/processresponseconsumebody=] set to |processResponse|.
 	</div>
 
-	Some legacy implementations preserved the original encoding of URLs
-	(as represented in the stylesheet)
-	and reproduced that encoding when communicating over the network.
-	UAs <em>must not</em> do this;
-	when it's necessary to re-encode a URL into bytes
-	to communicate over the network,
-	the URL must be encoded as UTF-8,
+	When [[url#percent-encoded-bytes|percent-encoding a URL]] from CSS for any purpose,
+	the UTF-8 encoding must be used
+	to produce the bytes to be encoded,
 	regardless of the original stylesheet encoding.
 
+
 <h2 id="numeric-types">
 Numeric Data Types</h2>