Examples: made examples's main.cpp consistent with returning 1 on error.

examples/example_sdl2_metal/main.mm

@@ -51,7 +51,7 @@ int main(int, char**)
     if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
     {
         printf("Error: %s\n", SDL_GetError());
-        return -1;
+        return 1;
     }
 
     // Inform SDL that we will be using metal for rendering. Without this hint initialization of metal renderer may fail.