Remove unnecessary Engine method (#4184)

* remove register_account_provider

* build rpc module

* new dummy client

rpc/src/v1/tests/eth.rs

@@ -116,7 +116,6 @@ impl EthTester {
 	fn from_spec(spec: Spec) -> Self {
 		let dir = RandomTempPath::new();
 		let account_provider = account_provider();
-		spec.engine.register_account_provider(account_provider.clone());
 		let miner_service = miner_service(&spec, account_provider.clone());
 		let snapshot_service = snapshot_service();