Update README.md

Add Kubernetes 1.31 as a supported version

Signed-off-by: Tomoki Sugiura <tomoki-sugiura@cybozu.co.jp>

Author: chez-shanpu

README.md

@@ -23,7 +23,7 @@ Version 2 is generally available (GA).  It conforms to [CNI spec 1.1.0](https://
 
 ## Dependencies
 
-- Kubernetes Version: 1.28, 1.29, 1.30
+- Kubernetes Version: 1.29, 1.30, 1.31
     - Other versions are likely to work, but not tested.
 
 - (Optional) Routing software