CI: protect against flaky network services

[chreekat]

https://github.com/p4lang/behavioral-model/actions/runs/24877155820/attempts/1

This workflow failed because the docker push action got a 502 from GitHub.

I opened docker/build-push-action#1522, but since GitHub has gotten less reliable recently, there may be other such cases.

We could consider trying out https://github.com/Wandalen/wretry.action to retry failed steps.