spec: fix assignments controller specs
spec: fix assignments controller specs

flag=none

Test Plan
- specs pass

Change-Id: If827338e2a6f12bb71b195e147e469a3a9477d8d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/230780
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Jeremy Neander <20252aad5efdc666f083d82ab63ed0f9f72a043e@instructure.com>
QA-Review: Gary Mei <4dff5ebcff9ed76793b70b9470ac64791a16ed11@instructure.com>
Product-Review: Gary Mei <4dff5ebcff9ed76793b70b9470ac64791a16ed11@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms