Remove superflous {type:string} from CodegenSchema (#46237)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46237

I can't find any uses of this, it's not referenced in any fixtures, and flow and typescript both pass without it.

Changelog: [Internal]

Reviewed By: makovkastar

Differential Revision: D61892355

fbshipit-source-id: 8ebb4da3e104109c740d90c2495dbcc89d3978e5