FIX do not exclude incoming_mail_attachment for external signatory book

...maarch_entreprise/actions/sendToExternalSignatureBook.php

src/app/action/controllers/ExternalSignatoryBookTrait.php

src/app/action/controllers/PreProcessActionController.php

...alSignatoryBook/controllers/MaarchParapheurController.php

...l/externalSignatoryBook/controllers/XParaphController.php