Fix link to <flag-icon> in acknowledgments

Closes whatwg#2977.

Author: a1626

source

@@ -121281,7 +121281,7 @@ INSERT INTERFACES HERE
 
   <div itemscope itemtype="http://n.whatwg.org/work">
    <p>The <code data-x="">&lt;flag-icon></code> example was inspired by <a itemprop="work"
-   href="https://customelements.io/stevenrskelton/flag-icon/">a custom element</a> by <a
+   href="https://github.com/stevenrskelton/flag-icon">a custom element</a> by <a
    itemprop="https://creativecommons.org/ns#attributionURL" href="http://stevenskelton.ca/">Steven
    Skelton</a>. (<a itemprop="license" href="https://opensource.org/licenses/MIT">MIT</a>)</p>
   </div>