fix some warnings (#660)

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

examples/component/modal_dialog_custom.cpp

@@ -8,7 +8,7 @@
 #include "ftxui/component/screen_interactive.hpp"  // for ScreenInteractive
 #include "ftxui/dom/elements.hpp"  // for operator|, Element, filler, text, hbox, separator, center, vbox, bold, border, clear_under, dbox, size, GREATER_THAN, HEIGHT
 
-int main(int argc, const char* argv[]) {
+int main() {
   using namespace ftxui;
   auto screen = ScreenInteractive::TerminalOutput();