Failed to compile with (llvm's) libc++ and C++23 due to missing `<exception>` include

[shenlebantongying]

Found in a project that vendors span: podofo/podofo#167

The root issue is that stdexcept no longer transitively includes exception for C++ > 20.

span/include/tcb/span.hpp

Lines 27 to 30 in 836dc6a

	#ifndef TCB_SPAN_NO_EXCEPTIONS
	#include <cstdio>
	#include <stdexcept>
	#endif

The llvm's libc++ code is here
https://github.com/llvm/llvm-project/blob/164597616c0c9cb42536d0d112e87e616751a438/libcxx/include/stdexcept#L280-L284

llvm's libc++ is the one shipped by apple on macOS.