Fix error C2397: conversion from 'const int' to 'unsigned __int64' requires a narrowing conversion

Except for iterators with exotic difference types:

For x64 algorithms, `_Diff` is naturally 64-bit, so `is_same_v<_Udiff, uint64_t>` is naturally taken.

But for x86 algorithms, `_Diff` is naturally 32-bit. If the URBG is 32-bit (or smaller),
then `_Udiff` will be `uint32_t`, and the `else` branch will be taken.

In that case, the error correctly complains that we're using braces
to convert from signed `_Diff _Index` to unsigned `_Uprod`, which is narrowing.
We should directly `static_cast` instead.

Author: StephanTLavavej

stl/inc/algorithm

@@ -6133,7 +6133,7 @@ private:
             const auto _Low = _Base128::_UMul128(_Ret, static_cast<_Udiff>(_Index), _High);
             return _Uprod{_Low, _High};
         } else {
-            return _Uprod{_Ret} * _Uprod{_Index};
+            return _Uprod{_Ret} * static_cast<_Uprod>(_Index);
         }
     }