xilem_web: Fix #465, by actually replacing the old element in the DOM-tree #921

Job	Run time
cargo check (aarch64-android)	1m 39s
cargo check (msrv) (wasm32)	28s
cargo check (msrv) (windows-latest)	3m 11s
cargo clippy (windows-latest)	6m 4s
cargo check (msrv) (macos-latest)	1m 47s
cargo clippy (wasm32)	1m 42s
cargo clippy (macos-latest)	3m 1s
cargo check (msrv) (ubuntu-latest)	1m 35s
cargo doc	1m 31s
cargo clippy (ubuntu-latest)	3m 40s
formatting	30s
cargo test (wasm32)	50s
cargo test (windows-latest)	4m 29s
typos	6s
cargo test (macos-latest)	2m 9s
cargo test (ubuntu-latest)	4m 7s
	36m 49s

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