update verbiage on recent feedback

fixes CNVS-995

test plan
 - on dashboard recent feedback should read "past
   two weeks" instead of "next two weeks"

Change-Id: Ic31055ef02c323b4c3899a1eba853afccd542f0c
Reviewed-on: https://gerrit.instructure.com/37299
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>