Drop OpenBSD system test CI job
The system tests on OpenBSD consistently exhibit lower stability compared to our other CI platforms. Some of these challenges are intrinsic to the system test itself and require attention. However, there are OpenBSD issues, which seem to be more widespread on this platform than others. In our daily CI pipelines, OpenBSD system tests often bear the brunt of all failed CI jobs.
It's possible that our OpenBSD CI image could be optimized, but we currently lack the domain-specific knowledge needed to make improvements.