pin ubuntu 23.04 in linux build engine

[mjhalwa]

generation of releases is configured in release.yaml. Currently linux releases are built with ubuntu-latest. The usage of (currently) latest Python version 3.11 requires at least ubuntu 23.04 and thus glibc version 2.35. Ubuntu 23.04 is currently the latest release of ubuntu. But soon there will be newer versions. Keeping ubuntu-latest in release.yaml will further increase the minimum glibc version required to run the executable.

Github - Actions - Available Images shows the currently available images. ubuntu-23.04 is not yet available. I recommend to regularly check the available images and when available pin ubuntu-latest to ubuntu-23.04.