games/supertuxkart: unbreak build with sdl2 >= 2.0.14

src/input/gamepad_config.cpp:35:1: error: static_assert failed due to requirement 'SDL_CONTROLLER_BUTTON_MAX - 1 == SDL_CONTROLLER_BUTTON_DPAD_RIGHT' "non continous name"
static_assert(SDL_CONTROLLER_BUTTON_MAX - 1 == SDL_CONTROLLER_BUTTON_DPAD_RIGHT, "non continous name");
^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PR:		253850
Approved by:	maintainer timeout (7 months)