Bump actions/checkout from 3 to 4 #1092

Job	Run time
Build benchmarks	34s
Minimum supported Rust version (no default features)	19s
Minimum supported Rust version (all features)	22s
Ubuntu (stable, no default features)	13s
Minimum supported Rust version (default features)	15s
Windows (stable, default features)	44s
Ubuntu (stable, all features)	20s
Ubuntu (stable, default features)	19s
Compute binary sizes	23s
Build documentation	7s
Ubuntu (nightly, no default features)	17s
Fuzz test (fill_first_fit)	3m 7s
Ubuntu (nightly, all features)	25s
Fuzz test (fill_optimal_fit)	3m 2s
Build Wasm demo	17s
Ubuntu (nightly, default features)	16s
Fuzz test (fill_fast_path)	3m 10s
Fuzz test (wrap_first_fit)	3m 1s
Fuzz test (wrap_optimal_fit)	3m 6s
Fuzz test (wrap_optimal_fit_usize)	3m 0s
Fuzz test (wrap_fast_path)	3m 0s
Fuzz test (unfill)	2m 59s
Fuzz test (refill)	2m 59s
Deploy Wasm demo	0s
	32m 15s

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