[FIX] Fix beam search test (vllm-project#2930)

tests/samplers/test_beam_search.py

@@ -26,6 +26,7 @@ def test_beam_search_single_input(
     max_tokens: int,
     beam_width: int,
 ) -> None:
+    example_prompts = example_prompts[:1]
     hf_model = hf_runner(model, dtype=dtype)
     hf_outputs = hf_model.generate_beam_search(example_prompts, beam_width,
                                                max_tokens)