Tests

Mutate == to != and vice versa #1127

Job	Run time
cargo-mutants	1h 21m 24s
incremental-mutants	11m 20s
build (macOS-latest, stable)	1m 59s
build (macOS-latest, nightly)	2m 44s
build (macOS-latest, 1.70)	3m 48s
build (ubuntu-latest, stable)	1m 23s
build (ubuntu-latest, nightly)	1m 54s
build (ubuntu-latest, 1.70)	1m 47s
build (windows-latest, stable)	2m 49s
build (windows-latest, nightly)	3m 21s
build (windows-latest, 1.70)	3m 25s
	1h 55m 54s

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