chore: Update method to access "secret_key_base" (#7337)

This will look at environment variables and Rails Credentials, and Rails Secrets.
See documentation here: https://api.rubyonrails.org/v7.0.5/classes/Rails/Application.html#method-i-secret_key_base

app/services/widget/token_service.rb

@@ -16,6 +16,6 @@ class Widget::TokenService
   private
 
   def secret_key
-    Rails.application.secrets.secret_key_base
+    Rails.application.secret_key_base
   end
 end