fix purity for dict.each #11325

Job	Run time
test-wasm	1m 15s
validate	12s
lint-build	49s
test (stable, x86_64-unknown-linux-gnu)	4m 5s
test (stable, aarch64-unknown-linux-gnu)	3m 38s
test (stable, x86_64-apple-darwin)	9m 40s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	9m 14s
rustfmt	7s
test (stable, x86_64-pc-windows-msvc)	5m 25s
test (stable, x86_64-unknown-linux-musl)	6m 33s
test (stable, aarch64-unknown-linux-musl)	4m 28s
test-projects	2m 33s
	47m 59s

Provide feedback