Bump treadle from `31867cb` to `8fa29df` (#146)

Bumps [treadle](https://github.com/freechipsproject/treadle) from `31867cb` to `8fa29df`.
- [Release notes](https://github.com/freechipsproject/treadle/releases)
- [Commits](https://github.com/freechipsproject/treadle/compare/31867cbce25a53c25b2d2a8639e1696121c391c9...8fa29df7661d494b6a6edbb63c45ab7de4abbb3d

)

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