submodule: bump openthread from `bb533e3` to `5290a2a` (#249)
submodule: bump openthread from `bb533e3` to `5290a2a` (#249)

Bumps [openthread](https://github.com/openthread/openthread) from `bb533e3` to `5290a2a`.
- [Commits](https://github.com/openthread/openthread/compare/bb533e34d3b517bd4897758fb70a20357fcaa9dd...5290a2aed014f7ddcf19df7948e4f336e93c2681)

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

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

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