This commit fixes issue #1529
This commit prevents nested w:pPr elements when using a ListItemRun with
a paragraph style. The different between a ListItem and a ListItem run
is that the setWithoutPPR method is called on the ParagraphStyleWriter
(PhpOffice\PhpWord\Writer\Word2007\Style\Paragraph).
According to the specs it's not allowed to have nested w:pPr elements.
See http://www.datypic.com/sc/ooxml/e-w_pPr-2.html