Invalidate DICOM-as-JSON summaries

Remove all the attachments of the type "DICOM-as-JSON" that are associated will all the DICOM instances stored in Orthanc. These summaries will be automatically re-created on the next access. This is notably useful after changes to the Dictionary configuration option. https://book.orthanc-server.com/faq/orthanc-storage.html#storage-area