CI(Github Actions): Remove attestation

Summary:
Not really needed, and causing build to ultimately fail.

Signed-off-by: Yongmin Hong <revi@omglol.email>

Test Plan: Build again.

Reviewers: O1 revi & automations, revi

Reviewed By: O1 revi & automations, revi

Differential Revision: https://issuetracker.revi.xyz/D136

.github/workflows/build-container.yml

@@ -43,9 +43,3 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-      - name: "Generate artifact attestation"
-        uses: actions/attest-build-provenance@v1
-        with:
-          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}
-          subject-digest: ${{ steps.push.outputs.digest }}
-          push-to-registry: true