submodule: bump openthread from `e0a1987` to `4fd20f7` (#50)
submodule: bump openthread from `e0a1987` to `4fd20f7` (#50)

Bumps [openthread](https://github.com/openthread/openthread) from `e0a1987` to `4fd20f7`.
- [Commits](https://github.com/openthread/openthread/compare/e0a1987336de203cdae30f06ff16cc2309817387...4fd20f7cf26201c69ab4e0700d461b84a8ce3e24)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-efr32,openthread/ot-efr32,openthread/ot-efr32