Remove grey outline on transparent animations #170

Job	Run time
Build Darwin executable / Build MacOS executable	1m 34s
Build Windows executable / Build Windows executable	1m 49s
Build Docker image & Linux executable (amd64) / Build linux and docker images	3m 37s
Build Docker image & Linux executable (arm64) / Build linux and docker images	19m 2s
Test on Darwin / Test on Darwin (apng)	1m 55s
Test on Darwin / Test on Darwin (gif)	1m 44s
Test on Darwin / Test on Darwin (png)	1m 55s
Test on Darwin / Test on Darwin (webp)	38s
Test on Windows / Test Windows (apng)	31s
Test on Windows / Test Windows (gif)	2m 1s
Test on Windows / Test Windows (png)	1m 35s
Run tests on Docker (arm64) / Run docker tests (apng)	1m 23s
Run tests on Docker (arm64) / Run docker tests (gif)	2m 20s
Run tests on Docker (amd64) / Run docker tests (apng)	29s
Run tests on Docker (arm64) / Run docker tests (png)	42s
Run tests on Docker (amd64) / Run docker tests (gif)	21s
Run tests on Docker (arm64) / Run docker tests (webp)	1m 46s
Run tests on Docker (amd64) / Run docker tests (png)	44s
Run tests on Docker (amd64) / Run docker tests (webp)	22s
	44m 28s

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