Move back to pypdf ?

[alexis-via]

according to https://pypdf2.readthedocs.io/en/latest/meta/CHANGELOG.html
we are invited to move back to pypdf, which is the most up-to-date and maintained now.
This lib is currently using PyPDF4.

A migration guide is given:
https://pypdf.readthedocs.io/en/latest/user/migration-1-to-2.html

This is an important change, that needs to be carefully studied before doing the switch.

[alexis-via]

done in 3.0 release