Tests

Mutate == to != and vice versa #1137

Job	Run time
incremental-mutants	15m 22s
build (macOS-latest, stable)	2m 35s
cargo-mutants	1h 14m 42s
build (macOS-latest, nightly)	2m 42s
build (macOS-latest, 1.70)	3m 44s
build (ubuntu-latest, stable)	1m 29s
build (ubuntu-latest, nightly)	1m 26s
build (ubuntu-latest, 1.70)	1m 47s
build (windows-latest, stable)	2m 56s
build (windows-latest, nightly)	2m 47s
build (windows-latest, 1.70)	3m 7s
	1h 52m 37s

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