Python: Update document generator demo README (#10386)

### Motivation and Context

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`AICodeSandbox` has updated their package name. A user also reached out
about whether it is possible to use models for the demo.

### Description

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1. Update the Document Generator demo README to reflect this change.
2. Update the README to include a note about using other models.

### Contribution Checklist

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- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
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raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Co-authored-by: Evan Mattson <[email protected]>

python/samples/demos/document_generator/README.md

@@ -37,7 +37,7 @@ To learn more about the Semantic Kernel Agent Framework, please refer to the [Se
 - `AICodeSandbox` - for executing AI generated code in a sandbox environment
 
     ```bash
-    pip install AICodeSandbox
+    pip install ai-code-sandbox
     ```
 
     > You must also have `docker` installed and running on your machine. Follow the instructions [here](https://docs.docker.com/get-started/introduction/get-docker-desktop/) to install docker for your platform. Images will be pulled during runtime if not already present. Containers will be created and destroyed during code execution.
@@ -54,6 +54,7 @@ OPENAI_API_KEY=<your-key>
 ```
 
 > gpt-4o-2024-08-06 was used to generate [GENERATED_DOCUMENT.md](GENERATED_DOCUMENT.md).
+> Feel free to use other models from OpenAI or other providers. When you use models from another provider, make sure to update the chat completion services accordingly.
 
 ```env