R1:68c687affdca

Fix call to undefined method PhutilJSON::encodeAsObject()

Summary:
Replace call to undefined method `PhutilJSON::encodeAsObject()` with existing `PhutilJSON::encodeFormatted()`

```
EXCEPTION: (Error) Call to undefined method PhutilJSON::encodeAsObject() at [<phabricator>/src/applications/transactions/xaction/PhabricatorEditEngineDefaultTransaction.php:68]
```

Closes T15603

Test Plan: Grep and read the code in https://we.phorge.it/source/arcanist/browse/master/src/parser/PhutilJSON.php

Reviewers: O1…