docs(advanced-tools): MCP documentation link for tool annotations (#8)

Author: kamranayub

exercises/01.advanced-tools/README.mdx

@@ -119,7 +119,7 @@ Clients can use annotations to:
 
 ### Learn More 📜
 
-For a full list of available annotations and their meanings, see the [official MCP documentation on tool annotations](https://modelcontextprotocol.io/docs/concepts/tools#tool-annotations).
+For a full list of available annotations and their meanings, see the [official MCP documentation on tool annotations](https://modelcontextprotocol.io/specification/2025-06-18/schema#toolannotations).
 
 ## Structured Output and Output Schemas