Use `relative_luminance` crate #1483

Job	Run time
Check Languages File	6s
Build --no-default-features (1.80 macOS-latest)	46s
Build --no-default-features (stable macOS-latest)	50s
Build --no-default-features --features color (1.80 macOS-latest)	51s
Build --no-default-features --features color (stable macOS-latest)	50s
Build --no-default-features (1.80 ubuntu-latest)	45s
Build --no-default-features (stable ubuntu-latest)	44s
Build --no-default-features --features color (1.80 ubuntu-latest)	50s
Build --no-default-features --features color (stable ubuntu-latest)	52s
Build --no-default-features (1.80 windows-latest)	44s
Build --no-default-features (stable windows-latest)	43s
Build --no-default-features --features color (1.80 windows-latest)	44s
Build --no-default-features --features color (stable windows-latest)	42s
Benchmarks	0s
Coverage ${{ matrix.feature-flags }} (${{ matrix.os }})	0s
Lint	0s
	9m 27s

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