[css-content-3] Update Changes list

Author: fantasai

css-content-3/Overview.bs

@@ -1358,6 +1358,8 @@ bookmark-state</h3>
 		<li>Prevent negative [=quote depth=] by ignoring excess closing quotes,
 			consistent with [[CSS2]].
 			(<a href="https://github.com/w3c/csswg-drafts/issues/2038">Issue 2034</a>)
+		<li>Defined computed value of ''content: normal'' for ''::placeholder'' and ''::file-selector-button''.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/6124">Issue 6124</a>)
 		<li>Miscellaneous editorial spec clean up.
 	</ul>