Only set TrimBox in postprocessing

Removes setting CropBox in PDF postprocessing, fixes https://gitlab.pagedmedia.org/tools/pagedjs-cli/issues/9

This box is already covered by TrimBox and is not recommend to use https://www.prepressure.com/pdf/basics/page-boxes

merged

By Fred Chasen on 2020-02-10T21:19:38 (imported from GitLab)

mentioned in commit 1110a754

By Fred Chasen on 2020-02-10T21:19:38 (imported from GitLab)