Bump chisel3 from `b169f6db` to `c21f31d0` (#367)

Bumps [chisel3](https://github.com/freechipsproject/chisel3) from `b169f6db` to `c21f31d0`.
- [Release notes](https://github.com/freechipsproject/chisel3/releases)
- [Commits](https://github.com/freechipsproject/chisel3/compare/b169f6db95f9778cf8968cc1042b7f810f9d8123...c21f31d09f2511497cea5cb03bd6ddba440c55fe

)

---
updated-dependencies:
- dependency-name: chisel3
  dependency-type: direct:production
...

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