windows packaging: reduce parallelism further to three
Some jenkins daily builders still run into issues from time to time, and
even at a reduced parallelism of three it doesn't affect overall
buildtime when building with just two or three languages and also not
when building with all languages. There might be a number of languages
where this has a penalty, but probably not a significant one.
Change-Id: I778b5fe21fe8f9bb1fcca1da3c4c0eeeda6c29d8
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/168403
Tested-by: Jenkins
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>