Fix typo in `allow-unused-imports` documentation #33747

Job	Run time
Determine changes	12s
pre-commit	38s
mkdocs	3m 0s
cargo fmt	18s
python package	1m 17s
benchmarks	5m 1s
cargo build (msrv)	3m 30s
cargo build (release)	5m 38s
cargo clippy	1m 50s
cargo fuzz	4m 56s
cargo shear	23s
cargo test (linux)	4m 5s
cargo test (wasm)	1m 37s
cargo test (windows)	8m 26s
formatter instabilities and black similarity	0s
test scripts	57s
ecosystem	8m 49s
test ruff-lsp	18s
Fuzz the parser	0s
	50m 55s

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