Fix deserialization of Bytes (#3866)

* Update impl-serde to patch RPC.

* Add test.

* Fix long line.

substrate/core/rpc/src/state/tests.rs

@@ -313,3 +313,11 @@ fn should_notify_on_runtime_version_initially() {
 		// no more notifications on this channel
 	assert_eq!(core.block_on(next.into_future()).unwrap().0, None);
 }
+
+#[test]
+fn should_deserialize_storage_key() {
+	let k = "\"0x7f864e18e3dd8b58386310d2fe0919eef27c6e558564b7f67f22d99d20f587b\"";
+	let k: StorageKey = serde_json::from_str(k).unwrap();
+
+	assert_eq!(k.0.len(), 32);
+}