Since commit ae0e830f, mirroring
is handled correctly in LO, so no need to handle it specially in
PDF import code. This obsolete handling causes double-mirroring.

Change-Id: Ia873f0426e444cafd80b24b7d209e90eb481d8f4
Reviewed-on: https://gerrit.libreoffice.org/21870Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>