Remove API key warning

[jackgerrits]

Thanks for catching this @robraux #3569 (comment)

Why are these changes needed?

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• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[robraux]

LGTM!