Update td_example.cpp (#1254)

Read the whole password, not only the first word from it

example/cpp/td_example.cpp

@@ -257,7 +257,7 @@ class TdExample {
             [this](td_api::authorizationStateWaitPassword &) {
               std::cout << "Enter authentication password: " << std::flush;
               std::string password;
-              std::cin >> password;
+              std::getline(std::cin, line);
               send_query(td_api::make_object<td_api::checkAuthenticationPassword>(password),
                          create_authentication_query_handler());
             },