Fix(Google GenAI Docs): Fix broken link

The link for the 'Gemini API Reference' in `google-genai-chat.adoc`
was pointing to an old URL and resulted in a 404 error.

This commit updates the URL to the correct destination.

Addresses reviewer feedback by updating all outdated links in the Google GenAI Chat documentation.
Specifically, corrected links for Gemini 2.0 Flash, Gemini 2.0 Flash-Lite, and Gemini Pro models.

Fixes #4758

Signed-off-by: MoGreene <13blueboy13@daum.net>

Author: Mo-Greene

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/chat/google-genai-chat.adoc

@@ -4,14 +4,14 @@ The https://ai.google.dev/gemini-api/docs[Google GenAI API] allows developers to
 The Google GenAI API supports multimodal prompts as input and outputs text or code.
 A multimodal model is capable of processing information from multiple modalities, including images, videos, and text. For example, you can send the model a photo of a plate of cookies and ask it to give you a recipe for those cookies.
 
-Gemini is a family of generative AI models developed by Google DeepMind that is designed for multimodal use cases. The Gemini API gives you access to link:https://ai.google.dev/gemini-api/docs/models/gemini/2-0-flash[Gemini 2.0 Flash], link:https://ai.google.dev/gemini-api/docs/models/gemini/2-0-flash-lite[Gemini 2.0 Flash-Lite], and link:https://ai.google.dev/gemini-api/docs/models/gemini-pro[Gemini Pro] models.
+Gemini is a family of generative AI models developed by Google DeepMind that is designed for multimodal use cases. The Gemini API gives you access to link:https://ai.google.dev/gemini-api/docs/models#gemini-2.0-flash[Gemini 2.0 Flash], link:https://ai.google.dev/gemini-api/docs/models#gemini-2.0-flash-lite[Gemini 2.0 Flash-Lite], and link:https://ai.google.dev/gemini-api/docs/models[Gemini Pro] models.
 
 This implementation provides two authentication modes:
 
 - **Gemini Developer API**: Use an API key for quick prototyping and development
 - **Vertex AI**: Use Google Cloud credentials for production deployments with enterprise features
 
-link:https://ai.google.dev/gemini-api/docs/reference[Gemini API Reference]
+link:https://ai.google.dev/api[Gemini API Reference]
 
 == Prerequisites