Fix comparison of integer expressions of different signedness (#121066)
Fixes these warnings
```
src/aten/src/ATen/native/cuda/ForeachReduceOp.cu:190:19: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const size_t’ {aka ‘const long unsigned int’} [-Wsign-compare]
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121066
Approved by: https://github.com/tringwald, https://github.com/Skylion007
