remove backwards compatible failed_jobs.original_id column

This was deprecated in a previous release.

closes CNVS-12828

test plan: failed jobs should still show in the UI properly and record
their original job id, including in rails3.

Change-Id: I0e8ff9af4e0d0aeb81dada3a91cad56c2b56bdac
Reviewed-on: https://gerrit.instructure.com/34359
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>