Fix IRFFT contrib op output dimension calculation (#15662)
### Description
Fixes the issue with IRFFT output dimension calculation as described in
#13236
### Motivation and Context
Please refer to #13236 for detailed description.
Specifically, [this code](https://github.com/microsoft/onnxruntime/blob/main/onnxruntime/contrib_ops/cuda/math/fft_ops.cc#L103) computes the output dimension as:
```
out_dim = in_dim * 2 - 1
```
while it should be this instead:
```
out_dim = 2 * (in_dim - 1)
```
(assuming the original signal has even number of samples, of course).
For example, if the original signal has 4 samples, then the round trip should look something like:
```
4 -> (one-sided RFFT) -> 3 (complex) -> (one-sided IRFFT) -> 4
```
with the current code the output will be a signal with 5 points.
---------
Co-authored-by: Alexey Kamenev <akamenev@nvidia.com>
Co-authored-by: Nick Geneva <nicholasgeneva@gmail.com>
