debug log readme docs incorrect

### System Info

https://github.com/meta-llama/llama-stack-client-python/blob/release-0.1.9/src/llama_stack_client/_utils/_logs.py#L19

the env var is a typo in the readme compared to the code

### Information

- [ ] The official example scripts
- [ ] My own modified scripts

### 🐛 Describe the bug

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### Error logs

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### Expected behavior

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