Please update https://github.com/Azure/azure-cli/blob/dev/doc/onboarding_guide.md

### Describe the bug

On behalf of carl.shipley@microsoft.com, Please remove Carl as the contact for our [Onboarding best practices](https://github.com/Azure/azure-cli/blob/dev/doc/onboarding_guide.md), and replace his name with the appropriate person. Thank you.

### Related command

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### Errors

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### Issue script & Debug output

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### Expected behavior

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### Environment Summary

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### Additional context

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