Fixed test pearson metric issue with old pytorch versions

Description:

Fixed test pearson metric issue with old pytorch version: 1.5.1, https://github.com/pytorch/ignite/actions/runs/8501889120/job/23285331993
```
     m = PearsonCorrelation()
    m.attach(engine, "corr")
```

  np_y = y.ravel().numpy()
E AttributeError: 'Tensor' object has no attribute 'ravel'

tests/ignite/metrics/regression/test_pearson_correlation.py:123: AttributeError



cc @kzkadc 

Restarted GHA PyTorch versions tests on this PR: https://github.com/pytorch/ignite/actions/runs/8505830753
- 1.5.1 is passing and others are failing due to https://github.com/pytorch/ignite/pull/3226

pytorch / ignite

Fixed test pearson metric issue with old pytorch versions #3225