Fix misaligned sections select in add people modal
Fix misaligned sections select in add people modal

fixes CNVS-39403

test plan:
  - as site admin, go to /accounts/1 (or whatever the right acct. id is)
  - click on + New Course and create a new course
  - click on the new course in the list of courses
  - click on People in the course's sidebar
  - click on + People button
  > expect the Add People modal to open with the Role and Section
  > dropdowns vertically aligned with each other, horizonally centered
  > in the modal

Change-Id: Ieff6d93923cd12b8567b97f618b92478d9e8508c
Reviewed-on: https://gerrit.instructure.com/126564
Tested-by: Jenkins
Reviewed-by: Felix Milea-Ciobanu <9384aa226ac9d3237ed0bc52e18ffcb251ee0bf7@instructure.com>
QA-Review: Anju Reddy <851202533fb1f0b615e4547ba226c76996d060dd@instructure.com>
Product-Review: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>

instructure/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms