rails3: stop testing for ErrorReport creation on 404s

We don't want these anymore, which is fortunate because they don't seem
to get created in rails3.

Change-Id: Ic6dd1e7a5dbf28cdb1e164ce9e27d7d427938f30
Reviewed-on: https://gerrit.instructure.com/30283
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>
QA-Review: Cameron Matheson <cameron@instructure.com>