[Misc] remove unused script (#15746)

Signed-off-by: reidliu41 <reid201711@gmail.com>
Co-authored-by: reidliu41 <reid201711@gmail.com>

python_only_dev.py

-# SPDX-License-Identifier: Apache-2.0
-
-msg = """Old style python only build (without compilation) is deprecated, please check https://docs.vllm.ai/en/latest/getting_started/installation.html#python-only-build-without-compilation for the new way to do python only build (without compilation).
-
-TL;DR:
-
-VLLM_USE_PRECOMPILED=1 pip install -e .
-
-or
-
-export VLLM_COMMIT=33f460b17a54acb3b6cc0b03f4a17876cff5eafd # use full commit hash from the main branch
-export VLLM_PRECOMPILED_WHEEL_LOCATION=https://wheels.vllm.ai/${VLLM_COMMIT}/vllm-1.0.0.dev-cp38-abi3-manylinux1_x86_64.whl
-pip install -e .
-""" # noqa
-
-print(msg)