Adding trunc to delta before passing to _format_timeframe.

[krisfremen]

Pull Request Checklist

Thank you for taking the time to improve Arrow! Before submitting your pull request, please check all appropriate boxes:

• [ ] 🧪 Added tests for changed code.
• [ ] 🛠️ All tests pass when run locally (run tox or make test to find out!).
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Description of Changes

Related to #789

[krisfremen]

Currently breaking some tests for granularity due to expectation of floats for some comparisons.

[jadchaar]

Any progress on this @krisfremen?

[jadchaar]

Closing this for now to clear up PRs, feel free to re-open it if you make new progress.