tests: Enable custom_sc_network feature

[lexnv]

Parts of our testing are guarded by "custom-sc-network", however cargo exposes custom_sc_network. This is a mismatch in feature naming.

litep2p/tests/conformance/substrate/mod.rs

Lines 21 to 30 in 59e194f

	#![cfg(feature = "custom-sc-network")]
	#[cfg(test)]
	mod connection;
	#[cfg(test)]
	mod notifications;
	#[cfg(test)]
	mod request_response;
	#[cfg(test)]
	mod websocket;

Further more, when enabling the feature its looks like the tests are using an outdated API and fail to compile

Discovered during: #207