Bugfix: Fix search for options provided as objects

We fixed a regression that was introduced in https://github.com/owncloud/owncloud-design-system/pull/1521.
`vue-select` automatically uses the property specified in `label` for filtering.
When custom filtering based on Fuse.js was introduced that functionality got lost.
Hence it was not possible to filter objects at all.


https://github.com/owncloud/owncloud-design-system/pull/1602