ops/numpy.py: support key as list in GetItem

When loading a model that contains GetItem nodes with multidimensional indices/slices as key, the key argument is loaded from JSON as a list, not a tuple (because JSON does not have the distinction).
So, treat the key list as equivalent to the key tuple. Copying is important, otherwise, the later pop() will remove the bound slice elements.

keras/ops/numpy.py

@@ -2695,6 +2695,8 @@ def compute_output_spec(self, x, key):
             remaining_key = [key]
         elif isinstance(key, tuple):
             remaining_key = list(key)
+        elif isinstance(key, list):
+            remaining_key = key.copy()
         else:
             raise ValueError(
                 f"Unsupported key type for array slice. Recieved: `{key}`"