Revert "[Peras 4] Add ObjectDiffusion and `PerasCert` diffusion (instance of ObjectDiffusion) (#1679)"
This reverts commit c0d8e62e452fdb4a5d8b06ca8bf5618709c1b4c7, reversing changes made to fe2513c5c888aba8f24f3b3136451b523d7a03ab.