Strange harvester bright/gama sprites when harversting

[yuri-ccp]

Hello, first I want to thanks @pchote for the excellent job giving us TD HD GFX to OpenRA.

I was play-testing the playtest-20221224-2 in my MacOS when I noticed that's there's strange bright/gama sprites during harvesters when they are harvesting tiberium, some sprites are more "brighter" than others as you can see in the appended screen video.

Gravacao.de.Tela.2023-01-03.as.5.17.19.PM.mov

[pchote]

This is a bug in the remastered assets themselves. I plan to fix this eventually by using the new mask feature to draw the harvester claws animating on top of the regular idle body.