Keep new line after the last dependency

If add a package with `yarn`, it will have a newline after the last
dependency so let's match with that.

railties/lib/rails/generators/rails/app/templates/package.json.tt

@@ -5,7 +5,7 @@
     "rails-ujs": ">=5.2.1"<% unless options[:skip_turbolinks] %>,
     "turbolinks": "5.1.1"<% end -%><% unless skip_active_storage? %>,
     "activestorage": ">=5.2.1"<% end -%><% unless options[:skip_action_cable] %>,
-    "actioncable": ">=5.2.1"<% end -%>
+    "actioncable": ">=5.2.1"<% end %>
   },
   "version": "0.1.0"
 }