chore: Remove unused gosquard

This was introduced in 34de45f, but has
not been used for several years.

Removing this will make the JS bundle smaller, improving the user
experience.

Author: mroderick

app/assets/javascripts/application.js

@@ -23,7 +23,6 @@
 //= require pickadate/picker.date
 //= require pickadate/picker.time
 //= require analytics
-//= require gosquared
 //= require subscriptions-toggle
 //= require invitations
 //= require cocoon