remove finding assets by non-signature

Change-Id: I757bd754466491aa0b1f1df2b8a5d0dcd5b355c4
Reviewed-on: https://gerrit.instructure.com/41376
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>