writerfilter: unused modelcleanup in ooxml

This script is not invoked by the build process and it just caused me
some headache when I thought it does something. Remove it to avoid 'git
grep' pollution next time.

Change-Id: Iaf4fdca12979a63178bead20fb1c96522a99822d

writerfilter/source/ooxml/modelcleanup

-#!/bin/sh
-#
-# This file is part of the LibreOffice project.
-#
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-#
-# This file incorporates work covered by the following license notice:
-#
-#   Licensed to the Apache Software Foundation (ASF) under one or more
-#   contributor license agreements. See the NOTICE file distributed
-#   with this work for additional information regarding copyright
-#   ownership. The ASF licenses this file to you under the Apache
-#   License, Version 2.0 (the "License"); you may not use this file
-#   except in compliance with the License. You may obtain a copy of
-#   the License at http://www.apache.org/licenses/LICENSE-2.0 .
-#
-
-(xsltproc modelcleanup.xsl model.xml | xmllint --format - > model.xml.tmp) && \
-mv model.xml.tmp model.xml