remove unused pipe dependency, fixes cargo deny #291

Job	Run time
cargo-deny	1m 25s
Test (windows-2022, x86_64-pc-windows-msvc)	28m 5s
Lint	6m 19s
Test (ubuntu-20.04, aarch64-linux-android, x86_64-unknown-linux-gnu)	8m 35s
Test (macOS-latest, x86_64-apple-darwin)	13m 22s
Test (ubuntu-20.04, x86_64-unknown-linux-gnu)	15m 50s
test_success	3s
	1h 13m 39s

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