[LLM] Update qwen examples

[Michaelvll]

Update the dependencies for qwen examples and minor fixes to the APIs called in the readme.

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
  • sky launch -c test-qwen qwen2-7b.yaml --cloud aws --use-spot

  curl http://$ENDPOINT/v1/chat/completions \
      -H "Content-Type: application/json" \
      -d '{
        "model": "Qwen/Qwen2-72B-Instruct",
        "messages": [
          {
            "role": "system",
            "content": "You are a helpful and honest code assistant expert in Python."
          },
          {
            "role": "user",
            "content": "Show me the python code for quick sorting a list of integers."
          }
        ],
        "max_tokens": 512
    }' | jq -r '.choices[0].message.content'

• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: conda deactivate; bash -i tests/backward_compatibility_tests.sh

[concretevitamin]

misaligned?