Remove old documentation re: SECURE_CRT

stb_image_write.h

@@ -10,11 +10,6 @@
 
    Will probably not work correctly with strict-aliasing optimizations.
 
-   If using a modern Microsoft Compiler, non-safe versions of CRT calls may cause 
-   compilation warnings or even errors. To avoid this, also before #including,
-
-       #define STBI_MSC_SECURE_CRT
-
 ABOUT:
 
    This header file is a library for writing images to C stdio or a callback.