Make the font a bit smaller

zig/sdl/hello_sdl.zig

    defer c.TTF_Quit();
    var font_file = if (args.len > 1) args[1] else "./FantasqueSansMono-Regular.ttf";
    const font = c.TTF_OpenFont(font_file, 20) orelse {
    const font = c.TTF_OpenFont(font_file, 16) orelse {
        c.SDL_Log("Unable to load font: %s", c.TTF_GetError());
        return error.TTFInitializationFailed;
    };