This method was calling `check_availability`, which returned a boolean
value and caused a `Naming/PredicateMethod` when upgrading rubocop.
So we're changing the logic a little bit to remove the
`check_availability` method and merge the tests of `check_availability`
and `notifiable_available?` (which were almost identical) together.
Usually when we use `try` we actually mean `try!`, which is the same as
the safe navigation operator. However, there are a few cases where we
actually mean to execute a method if the object responds to that method.
In those cases using `try` would actually be OK, but in order to avoid
confusion as to whether we mean to check for `respond_to?` or we mean to
use safe navigation, I'm removing all usages of `try`.
