The current code expects `active_record` to be loaded before `active_job`.
But I think there are no guarantees about load orders. At least,
`active_job` is loaded before `active_record` in a newer application.

In that case, `EnqueueAfterTransactionCommit` isn't loaded and an application
that uses `enqueue_after_transaction_commit` in jobs will fail with
the following error.

```
app/jobs/user_job.rb:2:in `<class:UserJob>': undefined method `enqueue_after_transaction_commit=' for class UserJob (NoMethodError)
```

I removed `active_record` hook to fix this. Active Record are onld used
inside methods in ``EnqueueAfterTransactionCommit`. So I think it's
safe to load the module without Active Record.