[V0 Deprecation] Remove unused output processor util (#25023)

Signed-off-by: Woosuk Kwon <woosuk@thinkingmachines.ai>

vllm/engine/output_processor/util.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-from typing import List
-from typing import Sequence as GenericSequence
-from typing import cast
-
-from vllm.model_executor.layers.sampler import SamplerOutput
-from vllm.sequence import CompletionSequenceGroupOutput, SequenceGroupOutput
-
-
-def create_output_by_sequence_group(
-        outputs: GenericSequence[SamplerOutput],
-        num_seq_groups: int) -> List[List[SequenceGroupOutput]]:
-    """Helper method which transforms a 2d list organized by
-    [step][sequence group] into [sequence group][step].
-    """
-    output_by_sequence_group: List[List[CompletionSequenceGroupOutput]] = [
-        [] for _ in range(num_seq_groups)
-    ]
-    for step in outputs:
-        sequence_group_output: CompletionSequenceGroupOutput
-        for i, sequence_group_output in enumerate(step):
-            output_by_sequence_group[i].append(sequence_group_output)
-
-    # Cast to the more generic type that CompletionSequenceGroupOutput
-    # inherits from.
-    return cast(List[List[SequenceGroupOutput]], output_by_sequence_group)