Remove deploy/cloudbuild-*.yaml files

[imjasonh]

As far as I can tell, these are unnecessary, since the equivalent build+push workflows are configured in GitHub Actions. I don't know at what point these became redundant, maybe someone else knows. @priyawadhwa do you know?

In any case, if they are in fact redundant, we should remove them before pushing another release, or else we may get a confusing race condition when pushing if the images aren't fully reproducible for some reason.

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Remove cloudbuild.yaml configs to build images; images are released using GitHub Actions.

[priyawadhwa]

My guess is that it was just accidentally left behind!