Update HashiConf alert-banner expiration (#1623)

Updates the HashiConf Alert Banner expiration to 10/20 @ 11pm (PT)

website/data/alert-banner.js

@@ -8,5 +8,5 @@ export default {
   linkText: 'Join Now',
   // Set the expirationDate prop with a datetime string (e.g. '2020-01-31T12:00:00-07:00')
   // if you'd like the component to stop showing at or after a certain date
-  expirationDate: '2021-10-21T12:00:00-07:00',
+  expirationDate: '2021-10-20T23:00:00-07:00',
 }