[cssom-1] Fix bikeshed warning for some <var>s being only used once.

Author: upsuper

cssom-1/Overview.bs

@@ -2038,7 +2038,8 @@ Note: The serialization of an empty CSS declaration block is the empty string.
 Note: The serialization of a non-empty CSS declaration block does not include any surrounding whitespace, i.e., no whitespace appears
 before the first property name and no whitespace appears after the final semicolon delimiter that follows the last property value.
 
-A <a>CSS declaration block</a> has these <a>attribute change steps</a> for its <a for="CSSStyleDeclaration">owner node</a>:
+A <a>CSS declaration block</a> has these <a>attribute change steps</a> for its <a for="CSSStyleDeclaration">owner node</a>
+with <var>localName</var>, <var>value</var>, and <var>namespace</var>:
 
 <ol>
  <li>If the <a for="CSSStyleDeclaration">readonly flag</a> is set, terminate these steps.