message: Fix clang-tidy error in "many cookie" tests".
diff: @@ -587,6 +587,7 @@ TEST_P(DownstreamProtocolIntegrationTest, LargeCookieParsingConcatenated) {
  {":authority", "host"},
  {"content-length", "0"}};
  std::vector<std::string> cookie_pieces;
  + cookie_pieces.reserve(7000);
  for (int i = 0; i < 7000; i++) {
  cookie_pieces.push_back(fmt::sprintf("a%x=b", i));
  }
  