fix type of super.prop in typed AST
fix type of super.prop in typed AST

Summary: the type of the whole member expression `foo.bar` is the type of the property, not the type of the object. however, the TAST for `super.prop` was using the type of `super` instead.

Reviewed By: samwgoldman

Differential Revision: D31958090

fbshipit-source-id: 9fab1a05da6ab966942aea5ff930c6137bbb3001

mroch/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,facebook/flow