R1:a7b2327c34ac

Fix an issue with "Auditors:" where an edge edit was used as a PHID list

Summary:
See <https://discourse.phabricator-community.org/t/runtimeexception-during-import-of-commit/3801>. When importing commits with "Auditors:", a raw transaction new value (with an edge edit map using a "+" key) may be passed as an unmentionable PHID list.

Instead, pass an actual PHID list.

Test Plan:
- Pushed a commit with "Auditors: duck".
- Ran daemons.
- Before patch: umentionable PHID exception.
- After patch…