Update header.html

Author: Andrew

_includes/header.html

@@ -113,7 +113,7 @@
 
 		<div class="site-header__utility">
 			{% if page.id == 'africa' %}
-			<a class="btn-alt" href="https://forms.gle/5jAoJbj5uJouvYBu9" target="_blank">
+			<a class="btn-alt" href="https://forms.gle/u1HUXBEPWA6JAp3R7" target="_blank">
 				<div>
 					<span>Join All In Africa</span>
 					{% include arrow.html %}