Allow arbitrarily long retraction

Marlin/Marlin_main.cpp

           SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
         }
         #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
-          if (labs(destination[E_AXIS] - current_position[E_AXIS]) > EXTRUDE_MAXLENGTH) {
+          if (destination[E_AXIS] - current_position[E_AXIS] > EXTRUDE_MAXLENGTH) {
             current_position[E_AXIS] = destination[E_AXIS]; // Behave as if the move really took place, but ignore E part
             SERIAL_ECHO_START();
             SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);