[css-grid] Update Changes list.

Author: fantasai

css-grid/Overview.bs

@@ -4314,6 +4314,7 @@ Changes</h2>
 			(<a href="https://github.com/w3c/csswg-drafts/issues/523">Issue #523</a>)
 		<li>Clarified definition of <a>min-size contribution</a>.
 			(<a href="https://github.com/w3c/csswg-drafts/issues/507">Issue #507</a>)
+        <li>Miscellaneous trivial fixes: broken references, typos, etc.
 	</ul>
 
 Privacy and Security Considerations {#priv-sec}