[libcxx] [clang] [libc++] Re-enable the clang_modules_include test for Objective-C++ (PR #66801)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> https://reviews.llvm.org/D158694

The motivation of my change is that I find multiple people are trying to fake `import std` from clang modules. This is not wanted. So I tried to ban it. I'll try to fix it or revert it later today if I didn't.

https://github.com/llvm/llvm-project/pull/66801