R1:b04d9fdc0ba8

Add a missing key to PhabricatorFile for destroying Files

Summary: See PHI176. Depends on D18733. We issue a query when deleting files that currently doesn't hit any keys.

Test Plan:
Ran `./bin/remove destroy --force --trace F56376` to get the query.

Ran ##SELECT * FROM `file` WHERE storageEngine = 'blob' AND storageHandle = '23366' LIMIT 1## before and after the change.

Before:

```
mysql> explain SELECT * FROM `file` WHERE storageEngine = 'blob' AND storageHandle = '23366' LIMIT 1;
+----+…