Created by: owjon
In v4-dev branch, the border-radius for progress bar component is applying $border-radius variable.
So currently we cannot customize the border-radius for progress bar without affecting other components which apply $border-radius variable as well . While there is a customizable variable $progress-border-radius not being in use at all (#18623 (closed)).
This commit changes to use $progress-border-radius to replace $border-radius for progress bar to make it work properly.