chore(ci): Update to `actions/checkout@v4` #1084

Job	Run time
Build benchmarks	29s
Minimum supported Rust version (no default features)	14s
Ubuntu (stable, no default features)	15s
Minimum supported Rust version (all features)	25s
Windows (stable, default features)	1m 26s
Ubuntu (stable, all features)	14s
Minimum supported Rust version (default features)	19s
Compute binary sizes	23s
Ubuntu (stable, default features)	19s
Ubuntu (nightly, no default features)	15s
Build documentation	16s
Build Wasm demo	17s
Ubuntu (nightly, all features)	22s
Fuzz test (fill_first_fit)	3m 5s
Ubuntu (nightly, default features)	19s
Fuzz test (fill_optimal_fit)	2m 59s
Fuzz test (fill_fast_path)	3m 5s
Fuzz test (wrap_first_fit)	2m 58s
Fuzz test (wrap_optimal_fit)	3m 3s
Fuzz test (wrap_optimal_fit_usize)	3m 4s
Fuzz test (wrap_fast_path)	2m 58s
Fuzz test (unfill)	3m 5s
Fuzz test (refill)	2m 58s
Deploy Wasm demo	0s
	32m 48s

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