[clang] [NFC] Minor fix to tryEmitAbstract type in EmitCXXNewAllocSize (PR #123433)

[Andy Kaylor via cfe-commits]

andykaylor wrote:

> Shouldn't there be a pointer-vs-intty difference in the LLVM-IR here?

No, because in this case tryEmitAbstract() is only using the size of the type that's passed in. After a few visits, it eventually calls this function:
```
  llvm::Constant *ProduceIntToIntCast(const Expr *E, QualType DestType) {
    QualType FromType = E->getType();
    // See also HandleIntToIntCast in ExprConstant.cpp
    if (FromType->isIntegerType())
      if (llvm::Constant *C = Visit(E, FromType))
        if (auto *CI = dyn_cast<llvm::ConstantInt>(C)) {
          unsigned SrcWidth = CGM.getContext().getIntWidth(FromType);
          unsigned DstWidth = CGM.getContext().getIntWidth(DestType);
          if (DstWidth == SrcWidth)
            return CI;
          llvm::APInt A = FromType->isSignedIntegerType()
                              ? CI->getValue().sextOrTrunc(DstWidth)
                              : CI->getValue().zextOrTrunc(DstWidth);
          return llvm::ConstantInt::get(CGM.getLLVMContext(), A);
        }
    return nullptr;
  }
```
The DestType parameter is only used to resize the constant if necessary (which in this case it won't be). The equivalent function in CIR was asserting that DestType was an integer type, which is what led me to this change.


https://github.com/llvm/llvm-project/pull/123433