test

Bump actions/cache from 2 to 4 #206

Job	Run time
Run the big ignored tests	44s
32bit tests	19s
Check formatting	6s
Build & test (ubuntu-latest, stable)	15s
Check it compiles on old Rust (1.31.0)	3m 25s
Clippy lints	19s
Verify benchmarks compile	20s
Build & test (ubuntu-latest, beta)	18s
Build & test (ubuntu-latest, nightly)	15s
Check documentation links	21s
Miri checks	28s
Build & test (macos-latest, stable)	40s
Check it compiles on old Rust (1.45.0)	15s
Thread Sanitizer checks MacOS	34s
Build & test (macos-latest, beta)	41s
Build & test (macos-latest, nightly)	29s
Build & test (windows-latest, stable)	1m 3s
Build & test (windows-latest, beta)	59s
Build & test (windows-latest, nightly)	43s
	12m 14s

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