Add comment for pydantic dependency

Author: pablomlago

requirements/requirements-llm.txt

@@ -7,6 +7,9 @@ onnx
 onnxruntime<1.21
 optimum[onnxruntime]
 pandas
+# TODO (pml): Remove when unpinning `transformers`, as `lighteval>=0.10.0`
+# requires this dependency explicitely.
+# See https://github.com/huggingface/lighteval/commit/2651750480d9a23ab0153f8ed3ef1d3331a2ea88.
 pydantic
 torch>=2.4
 tqdm