Portion of FileTreeRepositorySpec fails on GitHub Actions

[eed3si9n]

https://github.com/sbt/io/pull/303/commits/1597832c23d9a84799b1e0a9df1059e0a745c882

This part started to fail on GitHub Actions.

      withThread("file-deletion-thread") {
        subdirs.foreach(p => IO.delete(p.toFile))
      } {
        if (!deletionLatch.await(DEFAULT_TIMEOUT * 10)) {
          assert(deletionLatch.getCount == 0)
        }
        c.ls(dir.toGlob / AnyPath) shouldBe Symbol("empty")
      }

I suspect it's more to do with the CI environment of GitHub Actions (Docker container using ubuntu-latest?) than the actual code itself. Something to look into the future may be to create a directory somewhere that is not /tmp since Docker may be doing something weird with /tmp.