Drop OpenSUSE Leap 15.5 builders

Summary

Drop builders for OpenSUSE Leap 15.5, as it is being deprecated and removed from pipelines.

Related Issues

Related to omnibus-gitlab#8778 (closed)

Blocked by

Stop building OpenSUSE Leap 15.5 packages (omnibus-gitlab!8116 - merged) • Clemens Beck • 17.9