Fix a bug where some Maniphest batch edits were incorrectly skipped

Summary: Currently, if you have a task with project "X" and you apply a batch edit to it to remove "X", the action has no effect because we incorrectly skip the edit as a no-op. Instead, don't perform this check for edge edits.

Test Plan: Batch removed a project from several tasks with only one project.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Maniphest Tasks: T1566

Differential Revision: https://secure.phabricator.com/D3092