Correct column options presented in "Move tasks to project..." on workboards

Summary: Ref T13368. The column options presented to the user are currently incorrect because the wrong set of columns are drawn from.

Test Plan: On a workboard, used "Move tasks to project..." to target another board, saw that board's columns.

Maniphest Tasks: T13368

Differential Revision: https://secure.phabricator.com/D20698