Fix warnings related to panic and assert (#8272)

We were using the wrong syntax and that will be dropped with Rust 2021.
The compiler already starts to hint the wrong syntax with warnings. So,
we fix this here.

substrate/client/service/test/src/client/light.rs

@@ -684,10 +684,13 @@ fn changes_proof_is_generated_and_checked_when_headers_are_not_pruned() {
 		}).unwrap();
 
 		// ..and ensure that result is the same as on remote node
-		match local_result == expected_result {
-			true => (),
-			false => panic!(format!("Failed test {}: local = {:?}, expected = {:?}",
-									index, local_result, expected_result)),
+		if local_result != expected_result {
+			panic!(
+				"Failed test {}: local = {:?}, expected = {:?}",
+				index,
+				local_result,
+				expected_result,
+			);
 		}
 	}
 }

substrate/client/service/test/src/client/mod.rs

@@ -988,10 +988,13 @@ fn key_changes_works() {
 			None,
 			&StorageKey(key),
 		).unwrap();
-		match actual_result == expected_result {
-			true => (),
-			false => panic!(format!("Failed test {}: actual = {:?}, expected = {:?}",
-			                        index, actual_result, expected_result)),
+		if actual_result != expected_result {
+			panic!(
+				"Failed test {}: actual = {:?}, expected = {:?}",
+				index,
+				actual_result,
+				expected_result,
+			);
 		}
 	}
 }