[llvm] Fix C++23 error in {Succ,Pred}Iterator (#163555)
[1] calls insert in an underlying vector and in C++23 that requires the
iterators to satisfy stricter constraints [2][3].
[1]
https://github.com/llvm/llvm-project/blob/67e6a376209c9cc9576012c1c042bee9b852d584/llvm/lib/Analysis/LazyValueInfo.cpp#L333
[2]
https://github.com/llvm/llvm-project/blob/20bcf123e2db033f208462f34f63e292efbe0946/libcxx/include/__vector/vector.h#L645-L649
[3]
https://github.com/llvm/llvm-project/blob/20bcf123e2db033f208462f34f63e292efbe0946/libcxx/include/__algorithm/ranges_copy_n.h#L61
Co-authored-by: Victor Hugo Vianna Silva <victorvianna@google.com>
