Bump dev, adjust req. dependencies (#567)

packages/ui-keyring/src/Keyring.ts

@@ -1,8 +1,8 @@
 // Copyright 2017-2021 @polkadot/ui-keyring authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
-import type BN from 'bn.js';
 import type { KeyringPair, KeyringPair$Json, KeyringPair$Meta } from '@polkadot/keyring/types';
+import type { BN } from '@polkadot/util';
 import type { EncryptedJson } from '@polkadot/util-crypto/json/types';
 import type { KeypairType } from '@polkadot/util-crypto/types';
 import type { AddressSubject, SingleAddress } from './observable/types';