Fix docstring in DatasetDict::shuffle (#4344)

Author: felixdivo

src/datasets/dataset_dict.py

@@ -971,7 +971,7 @@ def shuffle(
                 If None, then fresh, unpredictable entropy will be pulled from the OS.
                 If an int or array_like[ints] is passed, then it will be passed to SeedSequence to derive the initial BitGenerator state.
                 You can provide one :obj:`seed` per dataset in the dataset dictionary.
-            seed (Optional `int`): A seed to initialize the default BitGenerator if ``generator=None``. Alias for seeds (the seed argument has priority over seeds if both arguments are provided).
+            seed (Optional `int`): A seed to initialize the default BitGenerator if ``generator=None``. Alias for seeds (a `ValueError` is raised if both are provided).
             generators (Optional `Dict[str, np.random.Generator]`): Numpy random Generator to use to compute the permutation of the dataset rows.
                 If ``generator=None`` (default), uses np.random.default_rng (the default BitGenerator (PCG64) of NumPy).
                 You have to provide one :obj:`generator` per dataset in the dataset dictionary.