The left mragin value is usually spelled out in RTF and DOCX, but this
bugdoc used the WW6 RTF markup to declare the numbering rules and there
the margin value was missing.

This also allows me to partially revert the changes to testTdf106953
from commit 56a695fd (tdf#112211 RTF
import: fix unwanted direct formatting for left indents, 2017-09-26).

Change-Id: I9902f2f9ada4080cb4d873624ae9824342c6ee77
Reviewed-on: https://gerrit.libreoffice.org/53364Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>