Use correct transaction types when creating diffs

Summary: See T10214 for context. These transaction types are obviously wrong as far as I can tell.

Test Plan:
Created a revision and didn't see an error in the daemon log.

```lang=php
<?php

require_once dirname(__FILE__).'/phabricator/scripts/__init_script__.php';

$yelirekim = (new PhabricatorPeopleQuery)
->setViewer(PhabricatorUser::getOmnipotentUser())
->withUsernames(['yelirekim'])
->executeOne();

$raw_diff = (new PhabricatorDifferenceEngine)
->generateRawDiffFromFileContent('oldfile', 'newfile');
$diff = (new ConduitCall('differential.createrawdiff', [
'diff' => $raw_diff,
]))
->setUser($yelirekim)
->execute();

$xactions = (new DifferentialDiffTransactionQuery)
->setViewer($yelirekim)
->withObjectPHIDs([$diff['phid']])
->execute();

foreach ($xactions as $xaction) {
echo $xaction->getPHID().':'.$xaction->getTitle().PHP_EOL;
}
```

for sanity

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: michaeljs1990, epriestley

Differential Revision: https://secure.phabricator.com/D15112