Fix `shadow_unrelated` in Xilem Core #2148

Job	Run time
cargo check (aarch64-android)	27s
cargo clippy (windows-latest)	3m 47s
cargo check (msrv) (wasm32)	16s
cargo clippy (macos-latest)	2m 7s
cargo check (msrv) (windows-latest)	4m 34s
cargo clippy (ubuntu-latest)	2m 9s
cargo check (msrv) (macos-latest)	51s
cargo check (msrv) (ubuntu-latest)	41s
cargo clippy (wasm32)	1m 25s
cargo doc	38s
formatting	31s
Prime LFS Cache	5s
cargo test (wasm32)	21s
typos	3s
cargo test (windows-latest)	4m 19s
cargo test (macos-latest)	1m 40s
cargo test (ubuntu-latest)	4m 48s
	28m 42s

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