description of problem here:
https://lists.freedesktop.org/archives/libreoffice/2017-July/078168.html

There is no need for a explicit delete of operator!= .
C++ doesn't generate comparison operators for objects even if one
kind is defined (here operator==).

Change-Id: Ifb22b3f9baa5ca23a4b64800d601cec66dcf39e0
Reviewed-on: https://gerrit.libreoffice.org/40566Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jochen Nitschke <j.nitschke+logerrit@ok.de>