Pass super() a Proc instead of Failure object

As of a recent [commit](https://github.com/rspec/rspec-expectations/blame/79582c2c160ac7b3a58d3d128012b022c63d6174/lib/rspec/matchers/built_in/raise_error.rb#L38) to rspec-expectations, Rspec::Matchers::BuiltIn::RaiseError strictly requires a Proc rather than something that quacks like one.