PDFBOX-1931: fix regression introduced in rev. 1562921, revert 2 lines to use Matrix.getXScale() as before, instead of AffineTransform.getScaleX() because its different

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1574961 13f79535-47bb-0310-9956-ffa450edef68