Fix minor error in doc

Not a big deal.

imgui.cpp

@@ -142,7 +142,7 @@
      // Load texture atlas (there is a default font so you don't need to care about choosing a font yet)
      unsigned char* pixels;
      int width, height;
-     io.Fonts->GetTexDataAsRGBA32(pixels, &width, &height);
+     io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
      // TODO: At this points you've got the texture data and you need to upload that your your graphic system:
      MyTexture* texture = MyEngine::CreateTextureFromMemoryPixels(pixels, width, height, TEXTURE_TYPE_RGBA)
      // TODO: Store your texture pointer/identifier (whatever your engine uses) in 'io.Fonts->TexID'. This will be passed back to your via the renderer.