docs: minor fix (three -> four) #1565

Job	Run time
Cargo Machete	1m 0s
Cargo Vendor	1m 3s
determine changes	6s
pre-commit	2m 58s
build binary \| linux x86_64	0s
build binary \| windows aarch64	0s
build binary \| macos aarch64	0s
build binary \| macos x86_64	0s
build binary \| windows x86_64	0s
cargo test \| macos aarch64	0s
cargo test \| ubuntu	0s
cargo test \| macos x86_64	0s
cargo test \| windows	0s
cargo rustdoc \| ubuntu	0s
Wheel Tests \| macos aarch64	0s
Wheel Tests \| linux x86_64	0s
Wheel Tests \| windows x86_64	0s
Downstream tests \| linux x86_64	0s
Downstream tests \| macos aarch64	0s
Downstream tests \| windows x86_64	0s
Integration tests \| linux x86_64	0s
Integration tests \| macos aarch64	0s
Pytest \| linux x86_64	0s
Integration tests \| windows x86_64	0s
Pytest \| macos aarch64	0s
Pytest \| windows x86_64	0s
	5m 7s

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