Remove libp2p dependency from sc-network-sync (#4974)

## Issue
https://github.com/paritytech/polkadot-sdk/issues/4858

## Description
This PR removes `libp2p::request_response::OutboundFailure` from
`substrate/client/network/sync/src/engine.rs`. This way, the dependency
with the library `libp2p` is removed from `sc-network-sync`.

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Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: Dmitry Markin <[email protected]>
Co-authored-by: Alexandru Vasile <[email protected]>