fix some warnings (#660)

Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

examples/dom/hflow.cpp

@@ -6,7 +6,7 @@
 #include "ftxui/dom/node.hpp"      // for Render
 #include "ftxui/screen/color.hpp"  // for ftxui
 
-int main(int argc, const char* argv[]) {
+int main() {
   using namespace ftxui;
   auto make_box = [](int dimx, int dimy) {
     std::string title = std::to_string(dimx) + "x" + std::to_string(dimy);