Bump third_party/openthread/repo from bf587dd to 33574ad

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `bf587dd` to `33574ad`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@bf587dd...33574ad)

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

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