Replace "an ui" with "a ui" #12896

Job	Run time
android	20s
Check wasm32 + wasm-bindgen	2m 37s
cargo-deny aarch64-apple-darwin	37s
cargo-deny aarch64-linux-android	36s
Check wasm32+atomics	1m 21s
cargo-deny i686-pc-windows-gnu	34s
cargo-deny i686-pc-windows-msvc	37s
cargo-deny i686-unknown-linux-gnu	36s
Format + check + test	5m 23s
cargo-deny wasm32-unknown-unknown	37s
cargo-deny x86_64-apple-darwin	36s
cargo-deny x86_64-pc-windows-gnu	37s
ios	22s
cargo-deny x86_64-pc-windows-msvc	41s
cargo-deny x86_64-unknown-linux-gnu	37s
Check Windows	2m 0s
cargo-deny x86_64-unknown-linux-musl	37s
cargo-deny x86_64-unknown-redox	35s
	19m 23s

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