provide correct selectedGroupId prop type

flag=none

test plan:
  - specs pass

qa risk: low

Change-Id: Ie76f0930218fa481ba95068f589dfe04ab72487d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/274055
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Omar Soto-Fortuño <omar.soto@instructure.com>
QA-Review: Omar Soto-Fortuño <omar.soto@instructure.com>
Product-Review: Omar Soto-Fortuño <omar.soto@instructure.com>

jest/jest-setup.js

@@ -81,7 +81,6 @@ const ignoredErrors = [
   /Invalid prop `outcomesGroup.contextId` of type `number` supplied to `FindOutcomesView`, expected `string`/,
   /Invalid prop `returnFocusTo` of type `DeprecatedComponent` supplied to `(CourseHomeDialog|HomePagePromptContainer)`/,
   /Invalid prop `selectedDate` of type `date` supplied to `CanvasDateInput`/,
-  /Invalid prop `selectedGroupId` of type `array` supplied to `GroupActionDrillDown`/,
   /Invalid prop `shares\[0\].content_export.id` of type `number` supplied to `ReceivedTable`/,
   /Invalid prop `submissions\[0\].submissionDraft.submissionAttempt` of type `number` supplied to `StudentsTable`/,
   /Invalid prop `value` of type `object` supplied to `CanvasSelect`/,

ui/features/outcome_management/react/shared/__tests__/GroupActionDrillDown.test.js

@@ -142,9 +142,7 @@ describe('GroupActionDrillDown', () => {
   })
 
   it('selects a group if selectedGroupId is provided', () => {
-    const {getByText} = render(
-      <GroupActionDrillDown {...defaultProps({selectedGroupId: ['101']})} />
-    )
+    const {getByText} = render(<GroupActionDrillDown {...defaultProps({selectedGroupId: '101'})} />)
     fireEvent.click(getByText('Groups'))
     expect(getByText('Leaf folder')).toBeInTheDocument()
   })