Enhancement: Input background color

The background color for input fields has been adjusted to better match with the overall design.

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
