Ignore touch audited callbacks globally

This is possible since audited 5.4.3, and IMHO it's useful because
audited has added a callback on touch, which could result in strange
behavior since we might use the `touch` method to expire the cache
without doing any changes.

While this doesn't affect our application because we're using the `on:`
option of the `audited` method in the budget investment model, it'll
make it easier to enable audited for other classes in custom
installations without having to worry about the (usually undesired)
touch callbacks.

config/initializers/audited.rb

@@ -1,3 +1,4 @@
 Audited.config do |config|
   config.audit_class = ::Audit
+  config.ignored_default_callbacks = [:touch]
 end