chore: Update array docs to use `u32` for the length type #14729

Job	Run time
build-nargo	2m 26s
build-noirc-abi	2m 10s
build-acvm-js	2m 6s
build-noir-wasm	4m 32s
ACVM JS (Node.js)	40s
ACVM JS (Browser)	1m 18s
noirc_abi	1m 21s
Noir JS	1m 6s
Example scripts	10s
noir_codegen	1m 13s
Check external repo - ${{ matrix.project.repo }}	0s
Integration Tests (Node)	2m 22s
noir_wasm	1m 40s
Integration Tests (Browser)	2m 11s
End	1s
	23m 16s

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