Tighten z safety check for pathological tracks (ATLASRECTS-8078)

Addresses failure ATLASRECTS-8078 due to some pathological track with a perigee with z=9369.77 mm. We're well beyond the tracking detectors at |z|=5000 mm, so we can be safer with this.

Still trying to understand which tool creates those pathological perigees to cut them at the source.

FYI @goetz