Remove xcode 15 workaround for boost (#39555)

Summary:
Remove Xcode 15 `_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION` workaround for boost. If we update boost, we don't need the workaround anymore.
This PR is based on https://github.com/facebook/react-native/issues/39552. Not sure how Meta internally deal with stacked PRs. This PR just adds a new commit based on https://github.com/facebook/react-native/issues/39552 anyway.

## Changelog:

[IOS][CHANGED] - Remove Xcode 15 `_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION` workaround for boost

Pull Request resolved: https://github.com/facebook/react-native/pull/39555

Test Plan: RNTester + Xcode 15

Reviewed By: cortinico

Differential Revision: D49454494

Pulled By: cipolleschi

fbshipit-source-id: aacabaa130b61598cf8bd206fdbb96d3b50ba74f