Remove some now-unneeded struct members

src/Backends/Rendering/OpenGL3.cpp

@@ -34,7 +34,6 @@ typedef struct RenderBackend_Surface
 	GLuint texture_id;
 	size_t width;
 	size_t height;
-	unsigned char *pixels;
 } RenderBackend_Surface;
 
 typedef struct RenderBackend_GlyphAtlas

src/Backends/Rendering/SDLTexture.cpp

@@ -18,7 +18,6 @@
 typedef struct RenderBackend_Surface
 {
 	SDL_Texture *texture;
-	unsigned char *pixels;
 	size_t width;
 	size_t height;
 	bool render_target;