Update SDL2 to version 2.28.1.

libs/SDL2/test/testlocale.c

@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
@@ -61,7 +61,7 @@ int main(int argc, char **argv)
         SDL_Quit();
     }
 
-   return 0;
+    return 0;
 }
 
 /* vi: set ts=4 sw=4 expandtab: */