Update the mpdf/mpdf library to ^8.0.0

Problem/Motivation

With the issue to add compatibility with the D10 we have to update the library mpdf/mpdf to ^8.0.0 to work correctly with php ^8.0.0 that is required by the D10.

Steps to reproduce

Try to run the composer require in a php ^8.0 server.

Proposed resolution

Upgrade the library mpdf/mpdf on composer.json to the ^8.0.0 version

Remaining tasks

User interface changes

API changes

Data model changes