remove focus when selecting submission criteria
remove focus when selecting submission criteria

In the Message Students Who modal, when using the enter key to select
"scored less than" and "scored more than" from the message type combo
box, the select box is still focused instead of the modal being
closed.

closes CNVS-35211

test plan:
- have a course with an assignment and student enrollments
- while using JAWS and IE 11, navigate to the Gradebook Individual View
- under Content Selection, choose an assignment to display
- under Assignment Information, click on the Message students who button
- once the widget is available:
  - press the down arrow to navigate to the Message Type drop down list
  - press the spacebar to select the Message Type
  - press the spacebar again to expand the list
  - use the down arrow to select "scored less than" or "scored more than"
  - press enter
  - verify focus the modal remains open

Change-Id: I0ea92b34399816cdd92bae7a317e930fa7107679
Reviewed-on: https://gerrit.instructure.com/105695
Reviewed-by: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>
Reviewed-by: Shahbaz Javeed <6692d7be3fa215e5483a121d6fb314def6049877@instructure.com>
Tested-by: Jenkins
QA-Review: Nathan Rogowski <2e8aa918660411855c6d44d5bb2da677aa033255@instructure.com>
Product-Review: Keith T. Garner <a1a80143a840c140f31c3495ebbd9ec906e09fed@instructure.com>

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