Revert "add digital climate strike banner"

This reverts commit 38a719b8d5.

site/src/template.html

@@ -16,8 +16,6 @@
 	<meta name='twitter:creator' content='@sveltejs'>
 	<meta name='twitter:image' content='https://svelte.dev/images/twitter-card.png'>
 
-	<script src="https://assets.digitalclimatestrike.net/widget.js" async></script>
-
 	<!-- Sapper generates a <style> tag containing critical CSS
 	     for the current page. CSS for the rest of the app is
 	     lazily loaded when it precaches secondary pages -->