fdo#63819 Ctrl+Backspace also deletes the space before the word

Change-Id: I147e8632c36ac0755a539d89ea5d34207839ea7c
Reviewed-on: https://gerrit.libreoffice.org/6518
Reviewed-by: Andrzej J.R. Hunt <andrzej@ahunt.org>
Tested-by: Andrzej J.R. Hunt <andrzej@ahunt.org>
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>