Updated "see also" references to be more consistent

Fixes https://github.com/libsdl-org/SDL/issues/9282

include/SDL3/SDL_filesystem.h

@@ -231,8 +231,6 @@ typedef enum
  *          folder, or NULL if an error happened.
  *
  * \since This function is available since SDL 3.0.0.
- *
- * \sa SDL_Folder
  */
 extern DECLSPEC char *SDLCALL SDL_GetUserFolder(SDL_Folder folder);