Use the non-deprecated importRoomKeys method on CryptoApi (#12232)

* Use the non-deprecated importRoomKeys method on CryptoApi

* Assert that we have crypto in import dialog

src/async-components/views/dialogs/security/ImportE2eKeysDialog.tsx

@@ -108,7 +108,7 @@ export default class ImportE2eKeysDialog extends React.Component<IProps, IState>
                 return MegolmExportEncryption.decryptMegolmKeyFile(arrayBuffer, passphrase);
             })
             .then((keys) => {
-                return this.props.matrixClient.importRoomKeys(JSON.parse(keys));
+                return this.props.matrixClient.getCrypto()!.importRoomKeys(JSON.parse(keys));
             })
             .then(() => {
                 // TODO: it would probably be nice to give some feedback about what we've imported here.