Change bridgeless check in dev menu (#43976)

Summary:
We would set the value of  _bridge ivar to bridgeProxy for turbo module in bridgeless mode in https://github.com/facebook/react-native/issues/43757 , so we need to change the way of bridgeless/bridge check.

## Changelog:

[IOS] [FIXED] - Change bridgeless check in dev menu

Pull Request resolved: https://github.com/facebook/react-native/pull/43976

Test Plan: Dev menu shows bridgeless/bridge mode correctly.

Reviewed By: christophpurrer

Differential Revision: D56056640

Pulled By: cipolleschi

fbshipit-source-id: 1358c3027c1d5f12c70dd4486cc1d5975c7a185a