Make backports.zoneinfo a normal dependency

[adamnovak]

This will fix #4969 by moving the dependency.

We also might want to cut the toil.lib.bioio to toil.test internal dependency.

Changelog Entry

To be copied to the draft changelog by merger:

• Toil now has correct dependencies for importing from toil.lib.bioio on Python 3.8.

Reviewer Checklist

• [ ] Make sure it is coming from issues/XXXX-fix-the-thing in the Toil repo, or from an external repo.
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    contrib/admin/test-pr otheruser theirbranchname issues/XXXX-fix-the-thing

  • [ ] If there is no associated issue, create one.
  • [ ] Read through the code changes. Make sure that it doesn't have:
  • [ ] Addition of trailing whitespace.
  • [ ] New variable or member names in camelCase that want to be in snake_case.
  • [ ] New functions without type hints.
  • [ ] New functions or classes without informative docstrings.
  • [ ] Changes to semantics not reflected in the relevant docstrings.
  • [ ] New or changed command line options for Toil workflows that are not reflected in docs/running/{cliOptions,cwl,wdl}.rst
  • [ ] New features without tests.
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Merger Checklist

• [ ] Make sure the PR passes tests.
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• [ ] Copy its recommended changelog entry to the Draft Changelog.
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