Add --bundle flag for cosign v4 compatibility

Cosign v4 requires --bundle when using --signing-config or the new
keyless OIDC flow. Add the bundle output to the sign-blob args.

Author: jeremy

.goreleaser.yaml

@@ -65,6 +65,7 @@ signs:
       - sign-blob
       - '--output-certificate=${certificate}'
       - '--output-signature=${signature}'
+      - '--bundle=${artifact}.bundle'
       - '${artifact}'
       - '--yes'
     artifacts: checksum