Update AI SDK model package installation link (#380)

Content seems to have moved.

Author: batjko

docs/src/content/docs/extensions/ai-sdk.mdx

@@ -27,7 +27,7 @@ of supported models that can be brought into the Agents SDK through this adapter
    npm install @openai/agents-extensions
    ```
 
-2. Choose your desired model package from the [Vercel's AI SDK](https://sdk.vercel.ai/docs/models/overview) and install it:
+2. Choose your desired model package from the [Vercel's AI SDK](https://ai-sdk.dev/docs/foundations/providers-and-models) and install it:
 
    ```bash
    npm install @ai-sdk/openai@"^1.0.0"