submodule: bump third_party/openthread/repo from ee2049f to `d31bce…

…e` (#2687)

Bumps [third_party/openthread/repo](https://github.com/openthread/openthread) from `ee2049f` to `d31bcee`.
- [Commits](openthread/openthread@ee2049f...d31bcee)

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

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