sorbet: fix `expect {}` arity error by reordering includes in RSpec shim

RSpec::Mocks::ExampleMethods includes ExpectHost which defines
`expect(target)` with a required argument. Because it was included
after RSpec::Matchers, it sat higher in the MRO and shadowed
`RSpec::Matchers#expect(value = T.unsafe(nil), &block)`, causing:

  expect { brew "command", "info" }  # Not enough arguments, expected 1 got 0

Fix by including RSpec::Matchers last so it sits above
RSpec::Mocks::ExampleMethods in the ancestor chain, making
the rspec-expectations signature take precedence:
https://github.com/rspec/rspec/blob/rspec-expectations-v3.13.5/rspec-expectations/lib/rspec/expectations/syntax.rb#L72-L74

brew tc error count: 3466 (was 3467)