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.

scripts/build_docker.sh

@@ -136,12 +136,10 @@ fi
 
 log "--- Building Docker image for $arch ($image_tag)"
 
-docker buildx build \
+docker build \
 	--platform "$arch" \
 	--build-arg "BASE_IMAGE=$base_image" \
 	--build-arg "CODER_VERSION=$version" \
-	--provenance true \
-	--sbom true \
 	--no-cache \
 	--tag "$image_tag" \
 	-f Dockerfile \