strings.h isn't available in Windows environments

I believe this header isn't necessary for clang-tidy, string.h has all the functions we care about.

Fixes https://github.com/libsdl-org/SDL/issues/12238

include/SDL3/SDL_stdinc.h

@@ -5969,7 +5969,6 @@ char *strdup(const char *str);
    their prototype defined (clang-diagnostic-implicit-function-declaration) */
 #include <stdio.h>
 #include <stdlib.h>
-#include <strings.h>
 
 #define SDL_malloc malloc
 #define SDL_calloc calloc