Tests

Mutate == to != and vice versa (#170) #1141

Job	Run time
cargo-mutants	1h 13m 43s
build (macOS-latest, stable)	2m 13s
incremental-mutants	0s
build (macOS-latest, nightly)	5m 18s
build (macOS-latest, 1.70)	2m 24s
build (ubuntu-latest, stable)	1m 37s
build (ubuntu-latest, nightly)	1m 59s
build (ubuntu-latest, 1.70)	1m 49s
build (windows-latest, stable)	3m 30s
build (windows-latest, nightly)	3m 51s
build (windows-latest, 1.70)	3m 20s
	1h 39m 44s

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