[css-pseudo-4] Use shorthand to make it slightly more obvious that it needs to be reset to be styled #9233

Author: fantasai

css-pseudo-4/Overview.bs

@@ -952,8 +952,8 @@ Default UA Styles</h3>
   The following additions are recommended for the default UA stylesheet:
   <pre class="lang-css">
     /* Represent default spelling/grammar error styling in an adjustable way */
-    :root::spelling-error { text-decoration-line: spelling-error; }
-    :root::grammar-error  { text-decoration-line: grammar-error; }
+    :root::spelling-error { text-decoration: spelling-error; }
+    :root::grammar-error  { text-decoration: grammar-error; }
   </pre>
 
   Some [=highlight pseudo-elements=]