[BE] Reformat ReduceOps (#91221)
Use curly braces even after single line `if`
Use whitespace between `if` and condition
Use `c10::irange`
Also, use `c10::multiply_integers` instead of explicit for loop of elements of `IntArrayRef`
Do not pass `num_input_dims` to `set_apparent_shapes` as it is always equal to the length of `input_shape` array
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91221
Approved by: https://github.com/kit1980, https://github.com/huydhn
