Call python as python3, as required by kubekins-e2e runner image

Author: tabbysable

config/jobs/kubernetes/sig-security/cve-feed-tests.yaml

@@ -14,7 +14,7 @@ presubmits:
       containers:
       - image: us-central1-docker.pkg.dev/k8s-staging-test-infra/images/kubekins-e2e:v20250905-c89b045f57-master
         command: ['runner.sh']
-        args: ['python', 'sig-security-tooling/cve-feed/hack/test_cve_title_parser.py', '-v']
+        args: ['python3', 'sig-security-tooling/cve-feed/hack/test_cve_title_parser.py', '-v']
         resources:
           limits:
             cpu: 1