On screen Flow rate doesn't work on U30 Pro/LK4 Pro

[mrv96]

Hi, after some trials i realized that your on screen flow option doesn't work. This because the extruder stepper speed is not updated in the code.

You should modify this lines:

https://github.com/LONGER3D/Marlin1.1.9_LGT0.3.x_Alfawise_Ux0Pro/blob/28744c771e2989d77efcfdd1bbbfc87522ad30eb/Marlin/LGT_SCR.cpp#L1404-L1406

in this way:

	case ADDR_VAL_FLOW:
		planner.flow_percentage[0] = Rec_Data.data[0];
		planner.refresh_e_factor(0);
		break;