Add display none

oops, hidden class doesn't exist, inline css display none

join.md

@@ -10,7 +10,7 @@ Our Slack is governed by the principles and rules in our [Community Guide](/comm
 
 <h3 class="marg-b-3">Please provide the following:</h3>
 <form class="join-form" method="POST" target="_blank" class="marg-b-4" data-netlify="true" action="/welcome" netlify-honeypot="bot-field">
-  <label class="hidden">
+  <label style="display:none">
     Don’t fill this out if you’re human: <input name="bot-field" />
   </label>
   <label class="marg-b-3" for="email">