Remove delete button in shared with others list

Whenever a file is shared with others or with link, a delete button used to be visible that triggered a direct deletion.
    
This button has been removed to avoid accidental deletion from people who might believe it was an unshare button. Unsharing is still possible inside the share dropdown.

Fixes https://github.com/owncloud/core/issues/11599

Please review @jancborchardt @MorrisJobke @icewind1991 @schiesbn