### Motivation and Context

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We are seeing exceptions in some samples due to a bug in the
`BaseTest.cs` module, that ignores the `modelName` parameter when
creating a kernel with chat completion.

### Description

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This PR ensures that the `modelName` parameter is consistently passed to
the `AddChatCompletionToKernel` method.

### Contribution Checklist

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- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄