spec: update test_after_commit

My fix was merged upstream.

Change-Id: I43f7b807f65cc738f930616f2a2ee685e78d0981
Reviewed-on: https://gerrit.instructure.com/43502
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: Brian Palmer <brianp@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>