[CUDA][Complex] Bump tolerances for TestFFTCUDA.test_reference_nd__refs_fft_irfftn_cuda_complex64 (pytorch#168016)

Otherwise we see e.g.,
```
Mismatched elements: 1 / 40320 (0.0%)
Greatest absolute difference: 0.0001373291015625 at index (0, 4, 0, 2, 3, 5) (up to 0.0001 allowed)
Greatest relative difference: 1.633889951335732e-05 at index (0, 4, 0, 2, 3, 5) (up to 1.3e-06 allowed)
```

Pull Request resolved: pytorch#168016
Approved by: https://github.com/nWEIdia, https://github.com/ezyang

Author: eqy

test/test_spectral_ops.py

@@ -357,6 +357,9 @@ def test_fft_half_and_chalf_not_power_of_two_error(self, device, dtype, op):
     @unittest.skipIf(not TEST_NUMPY, 'NumPy not found')
     @ops([op for op in spectral_funcs if op.ndimensional == SpectralFuncType.ND],
          allowed_dtypes=(torch.cfloat, torch.cdouble))
+    @toleranceOverride({
+        torch.cfloat : tol(2e-4, 1.3e-6),
+    })
     def test_reference_nd(self, device, dtype, op):
         if op.ref is None:
             raise unittest.SkipTest("No reference implementation")