flaky: e2e TestEGUpgrade/EnvoyShutdown

[shawnh2]

https://github.com/envoyproxy/gateway/actions/runs/8811709532/job/24187972908?pr=2665#step:6:17406

[shawnh2]

still fail: https://github.com/envoyproxy/gateway/actions/runs/9655504860/job/26631669933?pr=3599#step:6:19590

cc @guydc