This will only work if rspec-core is loaded.  rspec-mocks needs to be work standalone and it can't assume rspec-core is available.  In fact, given that this file has `extend(Mocks::Deprecation) unless respond_to?(:deprecate)` later on...this method definition will _only_ be used when rspec-core is _not_ loaded, in which case it will fail.

It should be written like `deprecate` above to construct a message and print it using `warn`.