Tweak pdf-filter-tokens to be less sensitive to floating point

Switch output to QDF for easier diffing
Simplify input image
Reduce decimal places

This works around an issue were, for certain versions, the mingw32
tests failed because of irrelevant floating point rounding issues in
the test output.

examples/pdf-filter-tokens.cc

@@ -204,6 +204,7 @@ main(int argc, char* argv[])
 
         QPDFWriter w(pdf, outfilename);
         w.setStaticID(true); // for testing only
+        w.setQDFMode(true);
         w.write();
     } catch (std::exception& e) {
         std::cerr << whoami << ": " << e.what() << std::endl;