Relaxed clippy fixes/nits (#2661)

This PR contains just a few clippy fixes and nits, which are, however,
relaxed by workspace clippy settings here:
https://github.com/paritytech/polkadot-sdk/blob/master/Cargo.toml#L483-L506

---------

Co-authored-by: Dmitry Sinyavin <dmitry.sinyavin@parity.io>
Co-authored-by: ordian <write@reusable.software>
Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/elections-phragmen/src/benchmarking.rs

@@ -38,7 +38,7 @@ fn endowed_account<T: Config>(name: &'static str, index: u32) -> T::AccountId {
 	let _ = T::Currency::make_free_balance_be(&account, amount);
 	// important to increase the total issuance since T::CurrencyToVote will need it to be sane for
 	// phragmen to work.
-	T::Currency::issue(amount);
+	let _ = T::Currency::issue(amount);
 
 	account
 }