Fix minor clippy lints in grandpa (#5988)

* grandpa: fix clippy lints about identity conversions

* grandpa: fix clippy lints about unwrap_or_default

* grandpa: fix clippy lints about explicit return

* grandpa: fix clippy lints about unnecessary intermediary

* grandpa: fix clippy lints about to_string

* grandpa: fix clippy lints about unused imports

* grandpa: fix clippy lints about increments

* grandpa: fix clippy lints about unnecessary matches

* grandpa: fix clippy lints about struct arguments

* Fix clippy::redundant_clone

* Fix clippy::clone_on_copy

* Fix clippy::or_fun_call

* Fix clippy::identity_conversion

substrate/client/finality-grandpa/src/communication/gossip.rs

@@ -887,7 +887,7 @@ impl<Block: BlockT> Inner<Block> {
 				// any catch up requests until we import this one (either with a
 				// success or failure).
 				self.pending_catch_up = PendingCatchUp::Processing {
-					instant: instant.clone(),
+					instant: *instant,
 				};
 
 				// always discard catch up messages, they're point-to-point
@@ -1281,7 +1281,7 @@ impl<Block: BlockT> GossipValidator<Block> {
 			inner: parking_lot::RwLock::new(Inner::new(config)),
 			set_state,
 			report_sender: tx,
-			metrics: metrics,
+			metrics,
 		};
 
 		(val, rx)