submodule: bump openthread from `20aee3f` to `a5eb1c9` (#331)
submodule: bump openthread from `20aee3f` to `a5eb1c9` (#331)

Bumps [openthread](https://github.com/openthread/openthread) from `20aee3f` to `a5eb1c9`.
- [Commits](https://github.com/openthread/openthread/compare/20aee3fa706d7936594f6decaf3747fc9166a166...a5eb1c9401d704482d2e9cc59d1fdd82137ec0fd)

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

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

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
openthread/ot-samr21,openthread/ot-samr21