build(deps): bump third_party/tools/slang from c9dd854 to a864e10

Bumps [third_party/tools/slang](https://github.com/MikePopoloski/slang) from `c9dd854` to `a864e10`.
- [Release notes](https://github.com/MikePopoloski/slang/releases)
- [Commits](MikePopoloski/slang@c9dd854...a864e10)

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

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