Omit unnecessary function call
Summary: As mentioned on rP8ce35e6b67e7e2a81b274bab7a6dd19dedb4df06, setConcreteOnly(true) can be omitted since (lacking magical powers) loadObjects() will always only instantiate concrete objects.
Test Plan: N/A
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: epriestley, Korvin
Differential Revision: https://secure.phabricator.com/D10050