Get the traverse test to work on GHC 9.4

[treeowl]

Something about the traverse test interacts really badly with either GHC 9.4 or a dependency we're getting when we use GHC 9.4, causing the test suite run to freeze. Frustrating experiments suggest:

1. There's some sort of deadlock going on. When the test suite freezes, it doesn't burn CPU or memory. If I read the output of ps right, it's waiting on ... something.
2. strace -f eventually starts spewing a ton of nearly identical calls. What they mean, I don't know.
3. The problem still shows up if we just generate the Seq and liftIO . print it. If we just generate it, things seem okay, I think.