Remove -1 px from LTI SR-Only elements
Remove -1 px from LTI SR-Only elements

Closes PLAT-4751
flag=none

Test Plan:
- Lanuch any LTI tool from the course navigation
- Verify the LTI iframd does not overlap the horizontal rule
  directly below the breadcrumbs

Change-Id: I695f576beb0559873418110e12396161d99979e0
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/229226
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Mysti Lilla <431d062aff1e8f25416b3a7b732fe6effdb03f9a@instructure.com>
QA-Review: Mysti Lilla <431d062aff1e8f25416b3a7b732fe6effdb03f9a@instructure.com>
Product-Review: Weston Dransfield <e9203059795dc94e28a8831c65eb7869e818825e@instructure.com>

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