Fix missing ID

Author: tabatkins

css-multicol-2/Overview.bs

@@ -2170,7 +2170,7 @@ Pagination and Overflow Outside Multicol Containers</h3>
 
 This appendix is <em>informative</em>.
 
-<h3 id="">Changes from the <a href="https://www.w3.org/TR/2024/WD-css-multicol-2-20241219/">First Public Working Draft</a> of 19 December 2024</h3>
+<h3 id="changes-from-20241219">Changes from the <a href="https://www.w3.org/TR/2024/WD-css-multicol-2-20241219/">First Public Working Draft</a> of 19 December 2024</h3>
 
 <ul>
 	<li>Removed the special case of 'column-rule-width' having a computed value of ''0'' when 'column-rule-style' is ''border-style/none'' or ''border-style/hidden''.