remove unused pipe dependency, fixes cargo deny #295

Job	Run time
Test (windows-2022, x86_64-pc-windows-msvc)	30m 20s
Test (ubuntu-20.04, aarch64-linux-android, x86_64-unknown-linux-gnu)	8m 13s
Test (ubuntu-20.04, x86_64-unknown-linux-gnu)	16m 20s
Lint	6m 23s
Test (macOS-latest, x86_64-apple-darwin)	10m 44s
cargo-deny	1m 16s
test_success	2s
	1h 13m 18s

Provide feedback