Fading color clip over color clip looks different beteween 19.12.3 and 22.08.1

Tested with kdenlive-19.12.3-x86_64.appimage, kdenlive-22.08.1-x86_x64.AppImage on Ubuntu 22.04.

To reproduce:

1. Open titles-19.12.3.kdenlive from erjiang/kdenlive-backcompat
2. Render out the project in both versions listed above
3. See that when the white clip fades in over the red clip, it looks darker in 19.12.3 compared to 22.08.1.