message: Use shared instead of unique ptr to avoid conversion
  Another case of addStreamDecoderFilter() taking a unique ptr, missed
  this one in the prev commit.
diff: @@ -14,7 +14,7 @@ Http::FilterFactoryCb Config::createFilterFactoryFromProtoTyped(
  const std::string&, Server::Configuration::FactoryContext&) {
  return [config](Envoy::Http::FilterChainFactoryCallbacks& callbacks) -> void {
  callbacks.addStreamFilter(
  - std::make_unique<Filter>(config.content_type(), config.withhold_grpc_frames()));
  + std::make_shared<Filter>(config.content_type(), config.withhold_grpc_frames()));
  };
  }
  