This fixes loads of warnings like this one:

warn:legacy.osl:22335:22335:writerfilter/source/dmapper/StyleSheetTable.cxx:1611: Exception in StyleSheetTable::getOrCreateCharStyle - Style::setPropertyValue

during import. They are harmless as we catch the exception, but they are
just noise. It seems the code that transforms grab-bag pseudo-props into
real props was added in commit 4c3ba3a4
(fdo#75757: Remove inheritance from std::map., 2014-07-26), which is
supposed to be a pure refactoring, so just remove this problematic
transformation.

Change-Id: Ibf45bfedc661f9e065405c47623516c4026148a4
Reviewed-on: https://gerrit.libreoffice.org/49105Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>