[css-shadow-parts-1] Fix example that was still using * and =>

Author: fergald

css-shadow-parts-1/Overview.bs

@@ -293,7 +293,7 @@ but never match additional <a>shadow-part pseudo-elements</a>.
     than is intended.
 
     If the <code>&lt;x-panel></code>'s internal confirm button had used something like
-    <code>part="confirm-button, * => confirm-*"</code>
+    <code>part="label => confirm-label"</code>
     to forward the button's internal parts up into the panel's own <a>part element map</a>,
     then a selector like
     ''x-panel::part(confirm-label)''