try diffing one product

Author: glbrntt

.github/workflows/soundness.yml

@@ -62,4 +62,4 @@ jobs:
             BASELINE_REF='${{ inputs.api_breakage_check_baseline }}'
           fi
           echo "Using baseline: $BASELINE_REF"
-          env GRPC_SWIFT_PROTOBUF_NO_PLUGIN=1 swift package diagnose-api-breaking-changes "$BASELINE_REF"
+          swift package diagnose-api-breaking-changes "$BASELINE_REF" --products GRPCProtobuf