update readme for vendor kernel

Author: amazingfate

README.md

@@ -1,4 +1,4 @@
 # Live iso for rk3588 based on debian live project
 [![image_build](https://github.com/amazingfate/rk3588-live-iso/workflows/Build/badge.svg)](https://github.com/amazingfate/rk3588-live-iso/actions/workflows/build.yml)
 
-# Live iso is using legacy 5.10 kernel packaged by armbian.
+# Live iso is using vendor 6.1 kernel packaged by armbian(now only for test use).