spec: fix sub-second precision error on mysql

refs CNVS-7032

Change-Id: I2f1913f08e8a3296eaacf83a3725bebeae81a99d
Reviewed-on: https://gerrit.instructure.com/28617
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>