Change header padding on external tool tray
Change header padding on external tool tray

The padding on the header of external tool tray is set by canvas,
not by the external content. This commit increases the padding
slightly to fix misalignment on the commons favorites tray.

Fixes LS-890
flag=none

Test plan:
 - Add commons app to an account
 - Go a course's assignments, click the menu at the top, click on
   'Commons Favorites'
 - Make sure the header is aligned with content like in ticket
   image

Change-Id: I4555f4cbc4eda4eb0be1f28eeb44a23cbddf058c
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/240604
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
QA-Review: Robin Kuss <0b206b54367b2de0334896ea45826f0e3194bd35@instructure.com>
Product-Review: Jackson Howe <318c10a818c1b1f2ec50cdcb1827b2c6c5ebd7dc@instructure.com>

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