Gemini updates

[apradoada]

PR to Address student concerns that the AI API Learn materials were out of date due to recent updates to Google Gemini. In general, the Gemini 1.5 Flash model has been deprecated in favor of Gemini 2.5 Flash. The package has also been renamed from google-generativeai to google-genai. The following specific changes have been made:

• Getting Ready to Use an AI API (getting-ready-to-use-ai-apis.md)

  • Removed references to Gemini 1.5 Flash.
  • Images and steps to set up an API key have been updated to reflect the current Gemini API documentation UI.
  • Callout was created for future cohorts to mention that the UI could change, but the steps will remain the same.

• Postman Environments (setting-up-ai-apis-postman.md)

  • Removed references to Gemini 1.5 Flash.
  • Updated images to reflect changes made to Postman Desktop Application.
  • Updated instructions to reflect changes to how and where Gemini includes API keys within a request.

• AI Models (ai-api-models.md)

  • Updated references from Gemini 1.5 Flash to Gemini 2.5 Flash
  • Updated references from google-generativeai to google-genai

• Text Completion Endpoints (text-completion-endpoints.md)

  • Updated references from Gemini 1.5 Flash to Gemini 2.5 Flash
  • Updated references from google-generativeai to google-genai

• Using the Gemini API (ai-apis-in-projects)

  • Updated references from Gemini 1.5 Flash to Gemini 2.5 Flash
  • Updated references from google-generativeai to google-genai
  • Updated steps within the NPC Generator walkthrough to match updated Gemini syntax.