remove (this: any) casts from the codebase
remove (this: any) casts from the codebase

Summary:
it's silly to hide errors by just casting to `any` and forgetting about it.
replace them with suppressions.

Reviewed By: pieterv

Differential Revision: D37478365

fbshipit-source-id: 5ea56890fba9fa78e9b47a8b7e868c7e8d862b1a

facebook/draft-js