Remove the flatten on actors to prevent delegator warning.

[jfvanderwalt]

Hi 👋 When using Flipper with actors that are ActiveRecord models, you get this warning whenever the application checks a feature flag:

...lib/flipper/feature.rb:103: warning: delegator does not forward private method #to_ary

There is a thread on the Rails Github issues explaining this particular issue, although this is not a big problem per se it does mean the Flipper gem generates unnecessary noise in application logs.

When the passing of multiple arguments was built in, the intent seems to have been to allow the users to pass arguments like:

Flipper.enabled?(:some_feature, [user, team, org])

In this case, the flatten does seem like it is not required and could be removed which eliminates the warning?