[css-color-4] Move note about missing values becoming 0, so it applies to both HTML-compatible and CSS serializations w3c#10550

Author: svgeesus

css-color-4/Overview.bs

@@ -6196,6 +6196,10 @@ Serializing sRGB values</h3>
 	the declared, computed and used value
 	is the corresponding sRGB value.
 
+	During serialization,
+	any [=missing=] values
+	are converted to 0.
+
 	<h4 id="HTML-compatible-serialization-of-srgb">HTML-compatible serialization of sRGB values</h4>
 
 	If the following conditions are all true:
@@ -6262,10 +6266,6 @@ Serializing sRGB values</h3>
 	with all <a href="https://infra.spec.whatwg.org/#ascii-lowercase">ASCII lowercase</a>
 	letters for the function name.
 
-	During serialization,
-	any [=missing=] values
-	are converted to 0.
-
 	For compatibility, the sRGB component values
 	are serialized in <<number>> form, not <<percentage>>.
 	Also for compatibility,