message: CXX-1256 Fix pool example URI
  Newer libmongoc has stricter connection string parsing.
diff: @@ -34,7 +34,7 @@ int main() {
  // respectively. Therefore, a mongocxx::instance must be created before using the driver and
  // must remain alive for as long as the driver is in use.
  mongocxx::instance inst{};
  - mongocxx::uri uri{"mongodb://localhost:27017?minPoolSize=3&maxPoolSize=3"};
  + mongocxx::uri uri{"mongodb://localhost:27017/?minPoolSize=3&maxPoolSize=3"};
  mongocxx::pool pool{uri};
  