[Color 4] Add specs for `color.is-powerless()` #1443

Job	Run time
Lint spec files	16s
Static analysis	18s
Unit tests	37s
JS API \| Pure JS \| Browser	1m 35s
Language \| Dart Sass \| Dart stable	1m 1s
JS API \| Pure JS \| Node lts/* \| ubuntu-latest	1m 17s
Language \| Dart Sass \| Dart dev	1m 3s
JS API \| Pure JS \| Node lts/* \| windows-latest	3m 11s
JS API \| Pure JS \| Node lts/* \| macos-latest	3m 49s
JS API \| Embedded \| Node lts/* \| ubuntu-latest	4m 40s
JS API \| Pure JS \| Node lts/-1 \| ubuntu-latest	1m 30s
JS API \| Embedded \| Node lts/* \| windows-latest	6m 41s
JS API \| Embedded \| Node lts/* \| macos-latest	7m 40s
JS API \| Pure JS \| Node lts/-2 \| ubuntu-latest	1m 49s
JS API \| Embedded \| Node lts/-1 \| ubuntu-latest	6m 28s
JS API \| Pure JS \| Node lts/-3 \| ubuntu-latest	2m 3s
JS API \| Embedded \| Node lts/-2 \| ubuntu-latest	6m 12s
JS API \| Embedded \| Node lts/-3 \| ubuntu-latest	1m 37s
	51m 47s

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