Revert "Add hideSelectionFromResult function"

This reverts commit 84cf134a4e889e5ac85641bb2ac732b015911174.

New problems found in:
https://github.com/ivaynberg/select2/issues/2196

Original issue:
https://github.com/ivaynberg/select2/issues/1538

Pull request:
https://github.com/ivaynberg/select2/pull/2032