[CI] skip vllm_example

[scv119]

Why are these changes needed?

vllm requires cuda to be build, which is not available in our CI gpu docker image.

No CUDA runtime is found, using CUDA_HOME='/usr/local/cuda'
--
  | Traceback (most recent call last):
  | File "/opt/miniconda/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
  | main()
  | File "/opt/miniconda/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 335, in main
  | json_out['return_val'] = hook(**hook_input['kwargs'])
  | File "/opt/miniconda/lib/python3.8/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 118, in get_requires_for_build_wheel
  | return hook(config_settings)
  | File "/tmp/pip-build-env-b4hl6g1_/overlay/lib/python3.8/site-packages/setuptools/build_meta.py", line 341, in get_requires_for_build_wheel
  | return self._get_build_requires(config_settings, requirements=['wheel'])
  | File "/tmp/pip-build-env-b4hl6g1_/overlay/lib/python3.8/site-packages/setuptools/build_meta.py", line 323, in _get_build_requires
  | self.run_setup()
  | File "/tmp/pip-build-env-b4hl6g1_/overlay/lib/python3.8/site-packages/setuptools/build_meta.py", line 338, in run_setup
  | exec(code, locals())
  | File "<string>", line 24, in <module>
  | RuntimeError: Cannot find CUDA at CUDA_HOME: /usr/local/cuda. CUDA must be available in order to build the package.

Also there is a bug in the build rule cc983fc#r119162333

Related issue number

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(