Update func azure functionapp publish documentation

The `func azure functionapp publish` command will now no longer display the function key in the URLs by default. A new option will soon be added that allows users to include the Function key from URLs displayed during deployment. The [docs](https://docs.microsoft.com/en-us/azure/azure-functions/functions-core-tools-reference?tabs=v2#func-azure-functionapp-fetch-app-settings) currently do not include this.

Open the linked Azure Functions Core Tools reference and locate the documentation for `func azure functionapp publish`. Confirm the current default URL behavior and update the command documentation to explain it, adding the new option once it is available; done means the reference matches the command's deployment output.

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