delay_keep_alive calls manage_heater and manage_inactivity

No need to call them again, the for-loop is very quick

Change in memory:
Flash: -10 bytes
SRAM: 0 bytes

Firmware/ultralcd.cpp

@@ -3207,9 +3207,6 @@ uint8_t lcd_show_multiscreen_message_with_choices_and_wait_P(
                 current_selection = LCD_BUTTON_TIMEOUT;
                 goto exit;
             }
-            manage_heater();
-            manage_inactivity(true);
-
             if (abs(enc_dif - lcd_encoder_diff) >= ENCODER_PULSES_PER_STEP) {
                 if (msg_next == NULL) {
                     if (third_choice) { // third_choice is not nullptr, safe to dereference