Docs: Fix invalid URLs in GenAI Chat doc

Addresses reviewer feedback by updating all outdated links in the Google GenAI Chat documentation.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 <[email protected]>

Author: Mo-Greene

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

@@ -4,7 +4,7 @@ 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: