Bump firrtl from `69b8a88` to `90fab5a` (#282)

Bumps [firrtl](https://github.com/freechipsproject/firrtl) from `69b8a88` to `90fab5a`.
- [Release notes](https://github.com/freechipsproject/firrtl/releases)
- [Commits](https://github.com/freechipsproject/firrtl/compare/69b8a88553247714ac82a778ed80c9a2f3491af9...90fab5ae6eab253723fab849e8723ad99d41909e

)

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

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