submodule: bump openthread from `f4b188d` to `f1fd52b` (#34)
submodule: bump openthread from `f4b188d` to `f1fd52b` (#34)

Bumps [openthread](https://github.com/openthread/openthread) from `f4b188d` to `f1fd52b`.
- [Commits](https://github.com/openthread/openthread/compare/f4b188d79dafdbde081497fcd116fa843fb2be37...f1fd52b9ef44931e782fc87a58c7f52cdd7d08bb)

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

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-cc2538,openthread/ot-cc2538