[JAX] Capped HuggingFace datasets version for TE/JAX encoder examples (#1940)

* capped JAX encoder example datasets version at below 4.0
Signed-off-by: Alp Dener <adener@nvidia.com>

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Signed-off-by: Alp Dener <adener@nvidia.com>

examples/jax/encoder/requirements.txt

-datasets
+datasets<4.0.0
 flax>=0.7.1
 nltk>=3.8.2
 optax

examples/jax/mnist/requirements.txt

-datasets
+datasets<4.0.0
 flax>=0.7.1
 optax
 Pillow