Remove SDL_config.h from the public headers

The SDL headers are no longer dependent on the build configuration.

Fixes https://github.com/libsdl-org/SDL/issues/6643 and https://github.com/libsdl-org/SDL/issues/6641

test/testautomation_mouse.c

@@ -1,8 +1,6 @@
 /**
  * Mouse test suite
  */
-
-#include <stdio.h>
 #include <limits.h>
 
 #include "SDL.h"
@@ -655,3 +653,5 @@ SDLTest_TestSuiteReference mouseTestSuite = {
     mouseTests,
     NULL
 };
+
+/* vi: set ts=4 sw=4 expandtab: */