AST-1621 Use Python modules from Ubuntu instead of latest version
Various latest Python modules, installed via pip, depend on jinja2-3.1.2, which breaks gcovr. Installing older versions using Ubuntu packages avoids the conflict and thereby fixes the pages job at the SKAO mirror of EveryBeam.
https://gitlab.com/ska-telescope/sdp/ska-sdp-func-everybeam/-/pipelines shows the fixed pipeline at the SKAO mirror.