Fix margin around school logo
Fix margin around school logo

in the process of fixing the global nav's focus, the school's logo at
the top lost the couple of pixels of margin around it.

fixes ADMIN-950
test plan:
  - change the canvas logo to the nmsu logo gif attached to the ticket
  > expect that it looks like the before screenshot, and not the after

Change-Id: I0bd2be2c56ce54d591929f841173834310ff5c1d
Reviewed-on: https://gerrit.instructure.com/146334
Tested-by: Jenkins
Reviewed-by: Jon Willesen <0321efbc0acf6204eb6035acb1d418838b450d08@instructure.com>
Reviewed-by: Mysti Sadler <431d062aff1e8f25416b3a7b732fe6effdb03f9a@instructure.com>
QA-Review: Jon Willesen <0321efbc0acf6204eb6035acb1d418838b450d08@instructure.com>
Product-Review: Erin Hallmark <2a4b17b11682b229726079a631360cf016a43450@instructure.com>

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