WS2-1649: fix(unity-bootstrap-theme): revert the removal of carousel image borders

[bebaps]

Description

Currently, in carousels, the images of the non-active items have their borders removed. This causes wired visuals when using images where the lack of a border is obvious. The XD does contain borders, and there is no explanation why the borders are being removed for these situations.

This PR restores the borders for the images.

Links

• JIRA ticket

Checklist

• [x] Unity project successfully builds from root yarn install & yarn build
• [x] Commits do not contain multiple scopes
• [x] No new console errors

Browsers

• [x] Chrome
• [x] Safari
• [x] Firefox