R1:b0d1d46a73f9

Drop the legacy hunk table

Summary: Ref T13054. Ref T8475. This table has had no readers or writers for more than a year after it was migrated to the modern table.

Test Plan: Ran migration, verified that all the data was still around.

Maniphest Tasks: T13054, T8475

Differential Revision: https://secure.phabricator.com/D19056