Bump verilator/master from 1df20f7 to a3d0cc6 (#646)

Bumps [verilator/master](https://github.com/verilator/verilator) from `1df20f7` to `a3d0cc6`.
- [Commits](verilator/verilator@1df20f7...a3d0cc6)

---
updated-dependencies:
- dependency-name: verilator/master
  dependency-type: direct:production
...

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