iOS Ruby Updates (#32456)

Summary:
Fix the `scripts/update-ruby.sh` so it always use the correct [bundle config](https://bundler.io/man/bundle-config.1.html#DESCRIPTION). In the current version it wasn't using the correct configuration inside the `template/` directory, resulting in incorrect platform for `template/Gemfile.lock`.

While at that, update the gems to their latest version:
- ethon 0.14.0 -> 0.15.0
- json 0.5.1 -> 0.6.0
- zeitwerk 2.4.2 -> 2.5.1
- bundler 2.2.28 -> 2.2.29

## Changelog

No changelog

Pull Request resolved: https://github.com/facebook/react-native/pull/32456

Test Plan:
Run `bump-oss-version.js` and see `template/Gemfile.lock` lists `ruby` as the `PLATFORM` (no diff in that line).

## References
 - https://github.com/facebook/react-native/commit/e18cf90d71d0bef2e2a0caf30a89e53129152965#r58230816

Reviewed By: yungsters

Differential Revision: D31841524

Pulled By: charlesbdudley

fbshipit-source-id: 695c245fcb344c866afed45f747e04233e5c91e4