message: Fix: `purser-core` genericWallet class internal flow types
  Public key and Derivation path flowtypes were overlooked when they
  were changed from normal props into getter only
diff: @@ -44,9 +44,9 @@ export default class GenericWallet {
  * Both `publicKey` and `derivationPath` are getters.
  */
  - publicKey: string;
  + publicKey: Promise<string>;
  - derivationPath: string;
  + derivationPath: Promise<string>;
  type: string;
  