fixes PLAT-1940
test plan:
create a grade passback with the timestamp between
0 and 60 seconds in the future.
it should not be rejected
create a grade passback with the timestamp more then 60 seconds in
the future
it should be rejected
Change-Id: Ica50c433efa0b7303a4031ab13f6edfebd5c73cd
Reviewed-on: https://gerrit.instructure.com/94251
Tested-by: Jenkins
QA-Review: August Thornton <august@instructure.com>
Reviewed-by: Andrew Butterfield <abutterfield@instructure.com>
Product-Review: Karl Lloyd <karl@instructure.com>