fix border radius on dashcards to match planner card radius / 4px
fix border radius on dashcards to match planner card radius / 4px

Fixes: UIDEV-143

test plan:
- navigate to the dashboard with card view selected
- ensure the dashcard border-radius is 4px

Change-Id: Ib747f9b6ff1723de5a309aea7be747059a6b8e99
Reviewed-on: https://gerrit.instructure.com/135380
Tested-by: Jenkins
Reviewed-by: Chris Hart <b82b40b84a2f06957ec9caf1768340bd6b929cc4@instructure.com>
QA-Review: Dan Sasaki <ae19fabf7fe19dff310008c9b6a4d2ec84d311d8@instructure.com>
Product-Review: Mary Jane Anderson <bfb9d3817d27ddfdcd2a6c0c878e2771b3b2c4a7@instructure.com>

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