build(deps): bump third_party/cctz from b6d7a85 to 2acd9f2

Bumps [third_party/cctz](https://github.com/google/cctz) from `b6d7a85` to `2acd9f2`.
- [Release notes](https://github.com/google/cctz/releases)
- [Commits](google/cctz@b6d7a85...2acd9f2)

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

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