Cleanup: remove stdio.h header from MEM_guardedalloc.h

This was included for `FILE *` which isn't used in the header.

Ref D10799

source/blender/blenkernel/intern/text_suggestions.c

@@ -22,6 +22,7 @@
  */
 
 #include <ctype.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>