Update degradations.py because of torchvision.transforms.functional_t…

…ensor deprecation in 2024 January

Since 2024 January v0.17.0 of torchvision, the module torchvision.transforms.functional_tensor is removed and the module torchvision.transforms.functional is available.
https://github.com/pytorch/vision/releases/tag/v0.17.0

The code is proposed by @Elawfant in this issue of BasicSR: XPixelGroup/BasicSR#677

vqfr/data/degradations.py

@@ -5,7 +5,13 @@
 import torch
 from scipy import special
 from scipy.stats import multivariate_normal
-from torchvision.transforms.functional_tensor import rgb_to_grayscale
+try:
+    from torchvision.transforms.functional import rgb_to_grayscale
+except ImportError:
+    try:
+        from torchvision.transforms.functional_tensor import rgb_to_grayscale
+    except ImportError:
+        raise ImportError("Failed to import rgb_to_grayscale from torchvision. Ensure you have a compatible version of torchvision installed.")
 
 # -------------------------------------------------------------------- #
 # --------------------------- blur kernels --------------------------- #