Remove white boarders from Shortcut Category icon

* The icon works with light mode, but breaks the UI with dark mode on.
* Previously, the icon would be show as a white square in dark mode.
* The new version shows it correctly, as a circle.

Test: manual
Flag: not needed

Change-Id: I61838266494a9a2c3048030ff3c95ced3db6347c
Fixes: 280069069