Remove `ProjectProfile->loadProfileImageURI()`

Summary: Ref T603. Gets rid of a sketchy, non-policy-aware, unbatched file query.

Test Plan: Looked at projects, typeahead, edited project profile images.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D7253