Update appsettings.json.openai-example

[stevemoser]

Motivation and Context

1. Following the README from a fresh project was broken when using the Open AI config as a starting point. So I updated with the new required model id key and replace the model with one that isn't deprecated: GPT-4.

Description

Config contained deprecated model ID and keys. Also added placeholder text for Org Id since it can't be blank just like the key field.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel-starters/blob/main/CONTRIBUTING.md)
• The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄