Bump chisel3 from `ffc4fb5b` to `6e7d1c59` (#199)

Bumps [chisel3](https://github.com/freechipsproject/chisel3) from `ffc4fb5b` to `6e7d1c59`.
- [Release notes](https://github.com/freechipsproject/chisel3/releases)
- [Commits](https://github.com/freechipsproject/chisel3/compare/ffc4fb5bff3edb6b3bd315cf7e2da91ba12e8b79...6e7d1c59769b09e967ab7a052772ae7a8c8b6c2a

)

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

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