[clang] [C23] Fix typeof handling in enum declarations (PR #146394)

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Sirraide wrote:

> > ```c++
> > typeof(int){} x; // Probably parsed as typeof(int{})
> > ```
> 
> GCC reject this https://godbolt.org/z/YEdnGh8T5

GCC rejects it in C mode; it accepts it in C++ mode.

https://github.com/llvm/llvm-project/pull/146394