Bump K8s version to 1.31 in EKS CI script (#7005)

This change is to bump up the EKS version to 1.31 in the CI script.

Signed-off-by: Wenying Dong <[email protected]>

Author: wenyingd

ci/test-conformance-eks.sh

@@ -22,7 +22,7 @@ function echoerr {
 
 CLUSTER=""
 REGION="us-west-2"
-K8S_VERSION="1.27"
+K8S_VERSION="1.31"
 AWS_NODE_TYPE="t3.medium"
 SSH_KEY_PATH="$HOME/.ssh/id_rsa.pub"
 SSH_PRIVATE_KEY_PATH="$HOME/.ssh/id_rsa"