Rubrics - Change "Find Outcome Criterion" to "Find Outcome"

Fixes CNVS-16760

Test Plan:

    - If necessary, add an outcome
    - Create/edit an assignment and click "Add Rubric"
    - Observe that the text next to the magnifying glass says "Find
      Outcome" instead of "Find Outcome Criterion"

Change-Id: I1026224351b1f4b6466de64bc26b230618431d51
Reviewed-on: https://gerrit.instructure.com/44060
Product-Review: Hilary Scharton <hilary@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Sean Lewis <slewis@instructure.com>