Removed code that no longer is needed (as far as i know)

Source/Urho3D/Resource/Image.cpp

@@ -37,8 +37,6 @@
 #include <STB/stb_image_write.h>
 #include "../DebugNew.h"
 
-//extern "C" unsigned char* stbi_write_png_to_mem(unsigned char* pixels, int stride_bytes, int x, int y, int n, int* out_len);
-
 #ifndef MAKEFOURCC
 #define MAKEFOURCC(ch0, ch1, ch2, ch3) ((unsigned)(ch0) | ((unsigned)(ch1) << 8) | ((unsigned)(ch2) << 16) | ((unsigned)(ch3) << 24))
 #endif