Bump firrtl from `b904cd0` to `264c538` (#153)

Bumps [firrtl](https://github.com/freechipsproject/firrtl) from `b904cd0` to `264c538`.
- [Release notes](https://github.com/freechipsproject/firrtl/releases)
- [Commits](https://github.com/freechipsproject/firrtl/compare/b904cd0c00f4f0d4fdfd9db90961aaf31aa191b3...264c5380ef390d9e6e3ae619c684453f75951d58

)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>