add test for destroy! in persistence tests

from looking at the code at [persistence.rb](https://github.com/rails/rails/blob/475c96589ca65282e1a61350271c2f83f0d4044f/activerecord/lib/active_record/persistence.rb#L151-L157) it looked like the `destroy!` method would not raise an exception... i still did not fully understand the defails, but i think it's black callback magic :sparkles: 

i see that there are already some tests for `destroy!` in `callbacks_test.rb` and `has_many_associations.rb`. nevertheless i think that this test should be in here as well.