Removed the vi format comments from the source

Vim users can use the [editorconfig plugin](https://github.com/editorconfig/editorconfig-vim) to automatically set tab spacing for the SDL coding style.

Fixes https://github.com/libsdl-org/SDL/issues/6903

src/stdlib/SDL_stdlib.c

@@ -664,5 +664,3 @@ int SDL_isblank(int x)
     return ((x) == ' ') || ((x) == '\t');
 }
 #endif
-
-/* vi: set ts=4 sw=4 expandtab: */