Tests

Don't save CI cache from secondary jobs, like mutants (#481) #1769

Job	Run time
quick-test	2m 28s
test (macOS-latest, stable)	4m 45s
test (macOS-latest, nightly)	6m 36s
test (macOS-latest, 1.78)	5m 22s
branch-mutants	0s
pr-mutants	0s
test (ubuntu-latest, stable)	4m 18s
test (ubuntu-latest, nightly)	5m 16s
cargo-mutants (0, cargo)	6m 6s
test (ubuntu-latest, 1.78)	4m 54s
tests-from-tarball (ubuntu-latest)	2m 12s
test (windows-latest, stable)	7m 42s
cargo-mutants (1, cargo)	7m 19s
test (windows-latest, nightly)	10m 54s
cargo-mutants (2, cargo)	6m 51s
test (windows-latest, 1.78)	8m 6s
cargo-mutants (3, cargo)	10m 9s
cargo-mutants (4, cargo)	9m 13s
cargo-mutants (5, cargo)	10m 22s
cargo-mutants (6, cargo)	8m 17s
cargo-mutants (7, cargo)	11m 46s
cargo-mutants (8, cargo)	9m 25s
cargo-mutants (9, cargo)	7m 2s
	2h 29m 3s

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