From now on, the choice between "PDFBox" and "command line" is made via a simple configuration, and no longer in the runtime file.xml
Modify the WEB-INF/param/runtime file .xml to remove the following line:
<org.ametys.plugins.flipbook.Document2ImagesConvertor>...</org.ametys.plugins.flipbook.Document2ImagesConvertor>
<org.ametys.plugins.flipbook.Document2ImagesConvertor>...</org.ametys.plugins.flipbook.Document2ImagesConvertor>
<org.ametys.plugins.flipbook.Document2ImagesConvertor>...</org.ametys.plugins.flipbook.Document2ImagesConvertor>