attestation: drop workflow check on core attestation

[woodruffw]

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This follows the workflow changes I made in homebrew-core:

• dispatch-build-bottle: add provenance step homebrew-core#171819
• dispatch-rebottle: add provenance homebrew-core#171986
• create-replacement-pr: add provenance homebrew-core#172005

With those changes, (hopefully) all of our bottle-uploading workflows now produce provenance. However, this means we no longer have a single workflow to verify on. As a result, this change relaxes the check to allow any attestation from Homebrew/homebrew-core, not just ones from the original publish workflow. I've left a detailed comment on how to ratchet this back down, but I figured I'd fix the verification failure first and then work on that 🙂

(This should not meaningfully impact the security model, since an attacker would still need to obtain access to an OIDC credential within the context of homebrew-core.)

[p-linnane]

Thanks!