Address rspec deprecation warnings fixes #1076

* `Mock` => `Double`
* `and_return { value }` => `and_return(value)`
* `be_false` => `be_falsey`
* `be_true` => `be_truthy`
* `config.infer_spec_type_from_file_location!` (we don't rely on this, but adding it silenced the last deprecation)