Remove an old Differential selection behavior


Remove an old Differential selection behavior

Ref T12822. Ref PHI878. This is some leftover code from the old selection behavior that prevented visual selection of the left side of a diff if the user clicked on the right -- basically, a much simpler attack on what ultimately landed in D20191.

I think the change from th to td "broke" it so it didn't interfere with the other behavior, which is why I didn't have to remove it earlier. It's no longer necessary, in any case.

Test Plan: Grepped for behavior name, selected stuff on both sides of a diff.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T12822

Differential Revision: https://secure.phabricator.com/D20196