submodule: bump openthread from 8a03257 to e43df01

Bumps [openthread](https://github.com/openthread/openthread) from `8a03257` to `e43df01`.
- [Release notes](https://github.com/openthread/openthread/releases)
- [Commits](openthread/openthread@8a03257...e43df01)

---
updated-dependencies:
- dependency-name: openthread
  dependency-version: e43df01933e45ecb492bbef954478761a40b935a
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]