Stop handling PosixException that is no longer thrown

[StefanSpieker]

Stop handling not used and deprecated PosixException which was thrown before Jenkins 2.339. But the pom has today a minimum Jenkins version of 2.426.3.
With a few other PRs we might be able to remove the PosixException from core.

Testing done

Ran tests locally

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[MarkEWaite]

Thanks!