upgrade to Spring AI 1.0.0-M8

Author: alexcheng1982

README.md

@@ -8,4 +8,4 @@ Reference implementation of [Agentic Workflow and Patterns](https://javaaidev.co
 Requirements:
 
 - Java 21 (for virtual threads)
-- Spring AI (Current version `1.0.0-M7`)
+- Spring AI (Current version `1.0.0-M8`)