remove reapZombies

remove reapZombies

Believed to be no longer needed as I've squashed the last ones.

Note that, in Test.Framework, I can see no reason for the code to have
run it twice. It does not cause running processes to exit after all,
so any process that has leaked and is running and causing problems with
cleanup of the directory won't be helped by running it.

This commit was sponsored by Mark Reidenbach on Patreon.