Images: Update kubectl to v1.31.5. (#12791)

Co-authored-by: Marco Ebert <[email protected]>

Author: k8s-infra-cherrypick-robot

images/test-runner/Makefile

@@ -50,7 +50,7 @@ image:
 		--build-arg BASE_IMAGE=${NGINX_BASE_IMAGE} \
 		--build-arg GOLANG_VERSION=${GO_VERSION} \
 		--build-arg ETCD_VERSION=3.5.13-0 \
-		--build-arg K8S_RELEASE=v1.29.2 \
+		--build-arg K8S_RELEASE=v1.31.5 \
 		--build-arg RESTY_CLI_VERSION=0.27 \
 		--build-arg RESTY_CLI_SHA=e5f4f3128af49ba5c4d039d0554e5ae91bbe05866f60eccfa96d3653274bff90 \
 		--build-arg LUAROCKS_VERSION=3.8.0 \
@@ -71,7 +71,7 @@ build: ensure-buildx
 		--build-arg BASE_IMAGE=${NGINX_BASE_IMAGE} \
 		--build-arg GOLANG_VERSION=${GO_VERSION} \
 		--build-arg ETCD_VERSION=3.5.13-0 \
-		--build-arg K8S_RELEASE=v1.29.2 \
+		--build-arg K8S_RELEASE=v1.31.5 \
 		--build-arg RESTY_CLI_VERSION=0.27 \
 		--build-arg RESTY_CLI_SHA=e5f4f3128af49ba5c4d039d0554e5ae91bbe05866f60eccfa96d3653274bff90 \
 		--build-arg LUAROCKS_VERSION=3.8.0 \