message: Update some fly_qgc_mission code comments
diff: @@ -112,8 +112,7 @@ int main(int argc, char **argv)
  {
  std::cout << "Uploading mission..." << std::endl;
  - // We only have the upload_mission function asynchronous for now, so we wrap it using
  - // std::future.
  + // Wrap the asynchronous upload_mission function using std::future.
  auto prom = std::make_shared<std::promise<Mission::Result>>();
  auto future_result = prom->get_future();
  mission->upload_mission_async(
  @@ -131,7 +130,7 @@ int main(int argc, char **argv)
  handle_action_err_exit(arm_result, "Arm failed: ");
  std::cout << "Armed." << std::endl;
  - // Before starting the mission, we want to be sure to subscribe to the mission progress.
  + // Before starting the mission subscribe to the mission progress.
  mission->subscribe_progress(
  [](int current, int total) {
  std::cout << "Mission status update: " << current << " / " << total << std::endl;
  @@ -155,11 +154,11 @@ int main(int argc, char **argv)
  sleep_for(seconds(1));
  }
  - // Lets wait for sometime.
  + // Wait for some time.
  sleep_for(seconds(5));
  {
  - // We are done, and can do RTL to go home.
  + // Mission complete. Command RTL to go home.
  std::cout << "Commanding RTL..." << std::endl;
  const Action::Result result = action->return_to_launch();
  if (result != Action::Result::SUCCESS) {
  