Enhancement: Remove border on buttons

The outer border for buttons has been removed. Outline buttons now have an inner outline instead.

https://github.com/owncloud/web/issues/7353
https://github.com/owncloud/web/issues/7373
https://github.com/owncloud/owncloud-design-system/pull/2345
https://github.com/owncloud/owncloud-design-system/pull/2352
https://github.com/owncloud/owncloud-design-system/pull/2354
