revert: "chore: enable SBOM attestation for image builds" (#16868)

Reverts coder/coder#16852

The CI failed to create the multi-arch manifest.

https://github.com/coder/coder/actions/runs/13773079355/job/38516182819#step:18:341

I personally think we should move to a [multi-arch
Dockerfile](https://docs.docker.com/build/building/multi-platform/#cross-compilation)
instead of creating the manifest manually.

.github/workflows/release.yaml

@@ -361,7 +361,6 @@ jobs:
           file: scripts/Dockerfile.base
           platforms: linux/amd64,linux/arm64,linux/arm/v7
           provenance: true
-          sbom: true
           pull: true
           no-cache: true
           push: true