fdo#70998 Use "Insert Image" in dialog as well

Change-Id: I598c7367806a88cd4e582333c1e2fc8b984333e5
Reviewed-on: https://gerrit.libreoffice.org/6561
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>