build(deps): bump third_party/tools/yosys from f20f913 to 8bc4bd8

Bumps [third_party/tools/yosys](https://github.com/YosysHQ/yosys) from `f20f913` to `8bc4bd8`.
- [Release notes](https://github.com/YosysHQ/yosys/releases)
- [Commits](YosysHQ/yosys@f20f913...8bc4bd8)

---
updated-dependencies:
- dependency-name: third_party/tools/yosys
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>