Exclude generated code from lint (#54530)

Summary:
I was experimenting with TS API in the monorepo, and spotted that root lint tries to format generated code.

This small change add exclusion for files in `private/react-native-codegen-typescript-test/lib` which are generated locally when running TS API tests. The path is already ignored in `.gitignore` file:
* https://github.com/facebook/react-native/blob/main/.gitignore#L146-L146

## Changelog:

[INTERNAL] [FIXED] - Exclude generated code from lint checks to avoid unnecessary warnings.

Pull Request resolved: https://github.com/facebook/react-native/pull/54530

Test Plan: Running `yarn lint` at monorepo root no longer outputs warnings.

Reviewed By: cortinico

Differential Revision: D86963479

Pulled By: cipolleschi

fbshipit-source-id: e067bbbbf69d24929095aed1145f41ae9f26fbd4