This expectation is prone to becoming a false positive if we ever change the wording.  I'd recommend we do one of two things:

* Change this line to `expect(RSpec).not_to receive(:warn_deprecation)`.  We don't expect any deprecation warning at all, right?
* Extract the regex into a local variable (in the scope of the example group) that both the positive (`expect().to receive`) and negative (`expect().not_to receive`) examples use rather than using a regex literal.