Update GPT model to GPT-4o

[PeterDaveHello]

Related to #67

Updates the AI model used in the code review process to GPT-4o.

• Model Configuration: Changes the default AI model in action.yml to "gpt-4o".
• Workflow Adjustment: Modifies .github/workflows/code_review.yml to use "gpt-4o" for the OpenAI API model during code reviews.

---

For more details, open the Copilot Workspace session.

[PeterDaveHello]

Please note that this PR was created by GitHub Copilot Workspace using #67 as its task

[villesau]

I think you also need to update the open-ai package.

[PeterDaveHello]

@villesau looks better now? 😄

[PierreGode]

Please @villesau review this soon, this will have a huge impact on pricing
gpt-4o Input $5.00 / 1M tokens Output $15.00 / 1M tokens
so half the price compared to GPT-4 Turbo.

[PierreGode]

@villesau are you alive mate?

[afsheen-gramx]

LGTM 👍