chore: Update Docker image signing step in workflow

.github/workflows/docker-publish.yml

@@ -78,13 +78,7 @@ jobs:
 
 
       # Sign the resulting Docker image digest except on PRs.
-      # This will only write to the public Rekor transparency log when the Docker
-      # repository is public to avoid leaking data.  If you would like to publish
-      # transparency data even for private images, pass --force to cosign below.
-      # https://github.com/sigstore/cosign
-      - name: Sign the published Docker image
-        if: ${{ github.event_name != 'pull_request' }}
-        env:
-          DIGEST: ${{ steps.build-and-push.outputs.digest }}
-          TAGS: ${{ steps.docker_meta.outputs.tags }}
-        run: cosign sign --yes "${TAGS}@${DIGEST}"
+      - name: Sign image
+        if: github.event_name != 'pull_request'
+        run: |
+          cosign sign -key cosign.key -a ${{ steps.build-and-push.outputs.digest }}